Related Local Links:
Fallout Shelters, Radiation..
Industar 61 lens (lanthanum glass)
Lens Faults Pages
Photo.Net on Radioactive Lenses (gamma levels..)
Radioactive Fed-5s (slight..)
Radioactive Optics Posting (WJM)
Radioactive Pentax Lens (GM tube sound file..)
Romancing the Rare Earths
On Enhancing Filters by Howard Ross
If you want to buy some slightly radioactive lenses and cameras, the U.S.
Government has a lot of them for sale -
cheap!. Maybe some of those bargains you got on EBAY are "hot" in a different sense than
you might have thought! I am assuming that heavily contaminated and
radioactive government surplus items end up in government low level
radioactive waste land-fills or other burial sites. So if your government
surplus bargain camera or lens is contaminated, it is probably only
"lightly" contaminated. That's good news, I guess?
Our main focus
here is not on contaminated lenses or cameras, but on naturally
radioactive or "hot" lenses due to the materials used in their
manufacture.
Other uses for rare earth elements in photography include color enhancing
filters. See Howard G. Ross' Romancing the Rare
Earths for a history of enhancing filters and the use of various rare
earth elements therein.
This decay process means these thoriated
glass lenses can gradually become more
radioactive
over time, as the more
highly radioactive decay products build up in the glass. This result is
counter-intuitive. You would expect the radioactivity to decrease
over time. But after chemically purifying the thorium from its ore
sources, the thorium is relatively free of these daughter products. Over
time, the thorium decays, and the levels of radioactive daughter
by-products builds up. Eventually a more highly radioactive equilibrium
will be reached, as in the original radioactive ores. So over the years,
your "hot" lenses are likely to get more radioactive rather than less.
Surprise!
Lanthanum has
two isotopes in its natural form, one of which is weakly radioactive.
Another source of rare earths such as lanthanum is cerite, which contains
the element cerium. Cheap glasses may have iron salts in them, often
yielding the familiar green color of some iron salt contaminated glasses.
Cerium is often added to glass to convert iron impurities into colorless
compounds, yielding clear glass suitable for optical uses. Unfortunately,
the rare earths include some chemically very similar elements as
contaminants, many of which are mildly radioactive.
The chemistry of lanthanum and its associated rare earths is so closely
related that it is readily possible to have radioactive contaminants end
up in the desired lanthanum salts used in making optical glasses. The
amount of such contaminants could also easily vary from batch to batch,
depending on the degree of contamination in the original monazite or other
mineral sources being used.
I don't think that the original levels of thorium or lanthanum specified for
use in these lenses [e.g., in patent filings] is the cause of their radioactivity.
Later lenses of the same exact design and glass formulas, but from later batches with
higher serial numbers, do not exhibit any similar degree of radioactivity. Nor do they
suffer from yellow discoloration over decades of time. So it isn't the thorium or the
lanthanum that causes the problem here. The radioactivity of these
early lenses is caused by contaminants in the ingredients (e.g., thorium salts) used to
make the early lenses. It is these radioactive contaminants which cause these lenses
to be more radioactive than their later (more purified) batches of the same design.
However, don't assume that all yellow lenses are necessarily radioactive. Many lenses turn
yellow due to aging of the Canada Balsam adhesives used to glue lenses
together. Other lenses may have coloration biases which make them
slightly yellowish rather than clear, or other colors depending on the glass. But if you have
a lens using early specialty glasses (wide angles, fast lenses..) from before the 1970s, you
should consider checking your lens for radioactivity. Most school physics labs can do this,
as can local Civil Defense offices and police or fire emergency response teams.
Another important point here is that these contamination levels vary from
batch to batch, depending on the contamination in the sands used to make
the impure chemicals being used. So you have to test each lens to
determine if it is radioactive, and how "hot" any given lens really
is. Tests of one lens from one batch won't apply to another lens made from
another batch of chemicals with different levels of radioactive contaminants.
You have to test each lens to be sure.
| Roger Hicks* on Radioactive Lenses: |
|---|
|
Radioactivity in the first generation of hot lenses c. 1941-1955 is a
by-product of imperfect refinement of the monazite sands used to provide
the rare earths. There are quite a few 'hot' rare-earth first-generation
lenses...
Radioactivity in the second generation of lenses was down to the use of
cerium to bleach iron salts in the glass; (colourless) ferrates are
stable in glass solution. Once again, the purity of the cerium was
questionable. These are alpha-particle emitters, which ain't normally a problem -- even a lens-cap stops the particles, as does a few cm of air -- but it's not a good idea to use the lens as a telescope eye-piece, as some did. These second-generation lenses stretched well into the 1960s; again from memory, at least one of the standard Takumars was 'hot'. |
Alpha particles can only go through a few inches of air, and are stopped
by a sheet of paper. But they can interact strongly with the surface of
the cornea of the eye held near the glass for long periods. This event
happens when an alpha particle emitter is used in the glass of a telescope
or microscope eyepiece. Such exposures can produce cancers and radiation
burns after long exposure and daily use.
Beta particles can
penetrate a few feet in air, or a range of thicknesses of cloth, paper,
and other materials. The beta particle emitters are most important
photographically. Beta particles can penetrate camera shutters and film
cassettes
to fog film next to radioactively "hot" lenses left in your camera bag.
Gamma and xrays can do so too, but their intensity is usually much less
from the contaminants in glass than for beta particles.
See our Ektar lenses pages for listing of some of
the many Ektar lenses that may be "hot", based on the above
observations. Similarly, see our 4x5" lens
pages for the APO-Lanthar lenses by Voigtlander and a listing of
Tessar derivatives. The "lanthar" in the
Voigtlander lens name evidently originated from the Lanthanum used to
create the needed high refractive index glasses needed for these
lens designs. Again, not all "Lanthar" lenses are necessarily radioactive,
since the term was used for marketing on many lenses, not all of which may
have used radioactive glass formulas.
| Lanthanum Glass in Widespread Use |
|---|
| There are an awful lot of lenses with lanthanum glass in them. Lanthanum crown glasses were developed by Morey at the NBS in the mid 1930's and developed commercially by Kodak who produced several Lanthanum glasses. They were applied to a wide variety of lenses by the 1940's including the Ektar series of Tessar type lenses. There are likely few lenses made in the last sixty years which do not contain some Lanthanum glass. It was one of the first high index-low dispersion glasses. |
The major direct impact of radioactivity on lenses is limited to the
accumulation
of particle tracks in the glass (especially from alpha particles). But
these changes can usually only be seen by microscopic examination. Some
radiation dose monitors use such particle tracks in special glasses to
monitor radiation levels in medical or military settings.
However, the early glass formulas and contaminated chemicals used have
produced lenses which have "yellowed" with age (see posts). This yellowing
is related to on-going chemical reactions in the lens related to the
chemistry of the early glass formulas used in high refractivity glasses.
See our lens color pages for tips on how to test
your lenses for this thorium glass yellowish coloration.
This photographic approach was how nuclear radiation was first detected
by Becquerel,
thanks to a fogged photographic plate placed near a sample of uranium ore.
The trick still works. You can also use a standard geiger muller counter
or other instrument able to detect beta and gamma rays.
The biggest real medical danger is to users of eyepieces of radioactive
glasses, where close proximity during long hours of viewing can result in
high dosages to the cornea of the eye.
As one poster below noted, the
nuclear plant where he worked tried to confiscate his "newer" Leica 35mm
f/2 summicron due to its "radioactive contamination". That's a danger of
another sort, but worth knowing about unless you don't mind your Leica
lenses ending up classified as "low level nuclear waste".
Another professional danger is potential fogging of film due to prolonged
close proximity in your camera bag between "hot" lenses and your
sensitive film stocks. Surprise!
Finally, I was firmly put down by some Leica collectors because the
official factory sources had denied that any Leica lenses were
radioactive. This stand was maintained despite a number of reports
confirming that tests had shown various Leica lenses were indeed
radioactive (e.g., 1.5 millirems). Turns out that the factory was well
aware of these "hot" or radioactive glass lenses, but Leitz management had
denied them for years (see postings below and LHSA articles).
So the final casualty here is the believability of various "published" and
"official" sources of information about lenses, which have denied that
their lenses were radioactive to any degree. Thanks to this page and these
posters and related articles and lens testing, we now know better. Chances
are rather good that if you have many older lenses from the mid-1960s and
before, that you have one or more radioactive glass lenses in your
collection.
Richard_Oesterling@lewishomes.com wrote:
> Looking through the manual I noticed that Konica states that it uses 'New > Rare Earth' in all of there lens designs. I believe that this means > 'Radioactive Material' as in the Lanthar glasses manufactured by > Voigtlander. This would make these lenses of APO design.
There is actually something to this. The Lanthanum (not to be confused
with Lanthar, a Voigtlander triplet-type lens design) "rare-earth"
(because of its classification on the periodic table of elements) glass
used in these post-war designes did have above-background levels of
radiation; I'm told it's low level/low energy stuff; not to
worry.
The high index/low disbursion post war glasses (many of which were
pioneered and produced by Kodak!) led to dramatic improvements in the
performance of tried and true designs such as tessar and heliar-types.
In fact, some tessar type designes which were recalculated post-war and
optimized for the better glasses were nearly APO. And of course lens
coatings made much more complicated designs possible.
To learn more about this fascinating area, check out any of several
Rudolf Kingslake books (some still in print)...
Eric Goldstein
From Koni Omega Mailing List;
Date: Mon, 16 Mar 1998
From: GRAPHIC@delphi.com
Subject: Re: [KOML] Lenses
re: radioactive glass Apparently, just because the elements are
radioactive, that does not mean that the lens was dsigned as an "apo-".
My reasoning is based on a recent article in Shutterbug about radioactive
glass that specifically sites the Asahi or Honeywell Pentax standard 50mm
lenses circa 1964. These were definitely not apo designs.
Wayne Catalano 504-271-1507 (voice and fax)
rec.photo.equipment.misc
From: "David Foy" nomail@this_address.please
[1] Re: Hot lenses???
Date: Fri Apr 03 11:04:15 CST 1998
Not only aerial lenses, but many lenses made with rare earth glasses are
radioactive. A prime example is the standard 50mm lens for the Canon
Pellix 35mm SLR. Shutterbug did an article on this sometime around a year
ago -- checking their annual index would point you toward it. You can test
for radioactivity by leaving the lens in the dark on a piece of enlarging
paper for a week, and then developing the paper.
Harmful? Apparently not, but you would want to be sure.
From: glosdl@email.uc.edu (David L. Glos)
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Aero Ektar (Was: Newton Photo Products LF Camera????)
Date: Mon, 26 Oct 1998
> I've never had an Aero Ektar to play with so can't testify from >personal experience. The explanation above doesn't quite make sense. >Most lenses intended for use in ordinary photography are corrected at >infinity. Generally they will have good performence down to some >limit like 10x focal length beyond which they will need to be stopped >down some. I don't know how the Aero Ektar could be different than >this. > I've also read suggestions that the color correction of this lens is >optimised toward the red since aerial cameras are nearly always used >with yellow filters and often used with IR material. If this is true >thei lens might exhibit some blue fringing. Someone who has a properly >mounted Aero Ektar might be able to say whether it does this. > This lens was intended for use in aerial reconnaissance, often with >hand-held cameras and for night flash photography where lens speed was >more important than exact geometry as in lenses meant for aerial >mapping. In other words, its design is more like an ordinary camera >lens than the usual aerial survey lens. It will be interesting to >hear from those who have practical experience. > There was also BTW a 12" version of this lens. It is a very >impressive piece of glass. >--- >Richard Knoppow >Los Angeles, Ca. >dickburk@ix.netcom.com
FWIW, I was recently given a 24"/6.0 Aero Ektar that is very impressive in
girth and weight. One of the elements in the rear group is yellow/brown in
color and will peg the meter on a geiger counter, if placed within 6".
Talked with several sources, including a retired military nuclear
engineer, and all said not to worry too much as it was emiting alpa
radiation from the trace of thorium (?) in the glass. I have yet to see
how it will image as I don't have a camera large enough to put it
on........and that includes an 8x10. On the barrel is an indication that
it will cover 9x18. Current thoughts center around a panorama camera from
hell, but backlog of projects exceeds time available to bring them to
fruition. I have also thought about making a nice telescope with the
beast.
BTW, I even talked with the Kodak person in charge of their historical
archive. He knew of the 6" and 12", and had examples on their shelves,
but had
no record of the 24".
David Glos
Univ. of Cincinnati
513.558.6930
glosdl@email.uc.edu
From: Peter De Smidt pdesmidt@fdldotnet.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Aeor Ektars Radioactive???
Date: Tue, 09 Mar 1999
DO1 wrote:
> I was recently informed that Aero Ektar lenses are radioactive > to the tune of 1 Mr per hour. Is this significant? If so, why would > the lenses be radioactive? > > Richard should have the answer for this. > > Thanks. Dan
According to Roger Hicks in Shutterbug, Aero Ektars emit gamma
radiation. It is because they used a radioactive type of glass, I can't
remember what kind. I heard that telescope eye pieces were also made of
a similar design, and these caused horrendous problems due to the
extended periods of close proximity. Don't keep an Aero Ektar near film
or paper, and don't sleep with it under your pillow, and you should
probably be ok. But I'm not a scientist, so check it out for yourself.
Take the lens to a place that can measure radiation, and see what they
can find out.
Regards,
Peter De Smidt
From: dickburk@ix.netcom.com (Richard Knoppow)
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Aeor Ektars Radioactive???
Date: Tue, 09 Mar 1999
>I was recently informed that Aero Ektar lenses are radioactive >to the tune of 1 Mr per hour. Is this significant? If so, why would >the lenses be radioactive? > > Richard should have the answer for this. > > Thanks. Dan
They contain some Thorium glass which is slightly radioactive.
Someone here once reported actually detecting this with a radiation
counter. It is not supposed to radiate any significant level.
The Thorium glass is also supposed to be a little unstable,
yellowing a little with age. This is meaningless in an aerial lens
which is typically used with a yellow filter anyway.
The Thorium glass had some desirable characteristic for getting the
optical performance wanted from these lenses and they were not
intended to have a long lifetime. However, there are a lot of Aero
Ektars around and they seem to be holding up just fine:-)
---
Richard Knoppow
Los Angeles, Ca.
dickburk@ix.netcom.com
From: "Mark Bergman" mb50742@navix.net
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Aeor Ektars Radioactive???
Date: Tue, 9 Mar 1999
Thorium is easily detectable with a 'beta' counter. I work in a nuclear
power plant and made the mistake of taking a 'newer' 35 F2.0 leica
summicron into the power block last winter. Everything coming out of the
power block is scanned for radiation and the assumption is if it is
radioactive it was dosed in the power block. It almost went to a rad
waste dump. However with a lot of work I was able to convince them the
radioactivity was fixed and a product of manufacture (some articles from
the Leica historical magazine helped).
IMHO (and the people whose job is to protect me from radiation on a daily
basis) the level was inconsequetional. Somewhere on the order of less
them
1 Mr. per hour (or 1/1000 of a rem). If you have a lens putting out 1 rem
an hour you better find the number for the NRC and call them immediately.
Sounds like Chernobyl.
[Ed. note: 5 rems is the USA lifetime worker exposure limit, so at 1
millirem/hr, it would take 5,000 hours of exposure to accumulate such an
exposure, or circa 200 days exposure. This level is actually pretty high
for
gamma radiation, if true, IMHO. Shielding or distance can both be used to
reduce the received radiation dose. ]
From Leica User Group:
Date: Tue, 24 Aug 1999
From: "Doug Richardson" doug@meditor.demon.co.uk
Subject: [Leica] Yellowing glass in retractable Summicron
We've had a lot of discussion on the subject of the possible use of
radioactive thorium-based glass in some Leitz lenses.
Bill Rosauer wrote:
Hold your LTM Summicron over a white piece of paper and look through
it.
If the lens has a yellowish cast, this is most certainly one of the early
Summicrons in which radioactive thorium was one of the "rare" earth
elements used in making the glass. Apparently, this warm yellowish cast is
part of the decaying process of the thorium.
On Sunday I tried this test with my own recently-purchased 5cm
retractable Summicron, and yellow it most certainly is. No point in
trying to shoot Kodachrome with this one!
Does anyone know is this type of glass was used in all 5cm retractable
Summicrons?
Regards,
Doug Richardson
From Leica Mailing List
Date: Thu, 27 Jan 2000
From: Amilcar de Oliveira amilcar@domain.com.br
Subject: Re: [Leica] Summicron Radioactive elements - LHSA
Viefinder
1.5 milliroentgen is nominally less than the MPD (maximum permissible dose
for radiation workers) established by the US National Council on Radiation
Protection and Measurements. The MPD was 0.2 roentgen in 1931 and has been
lowered in three occasions. Now it is 0.02 roentgen per workday. I used
the word "nominally" because the way cameras are used, some parts of the
body will receive more radiation and I think the standard is for whole
body exposure. I caution that trying to arrive at conclusions from a
single number like 1.5 mR is even riskier than trying to assign a single
numerical score to a lens. There are many factors at work here, i.e. the
camera body itself will give a measure of protection, the lens cap may
also help protect the photographer when the camera is not in use,
different organs will have different sensitivities to radiation and many,
many other things. So it's very hard to estimate the real absorbed dose.
Dr. Amilcar de Oliveira
Oral Radiology
Rio de Janeiro
MGMcGough@aol.com wrote:
> The LHSA VF article by Bill Gordon was a follow up on the findings by Dr. > Cyril Blood of the British LHS. Gordons test of the half dozen Summicrons > with S/Ns under 1,000,000 showed that the average front element emitted > 1.5 miliroengtens and if laid front down on an unexposed piece of film, > would leave a dark circle after about one week. This is far less radio- > activity then the radium dial wrist-watches of the past. I dont mean the > calcium disulfide luminous type but the radium dial Omegas & Rolexs. > > For many years, the Leitz management denied using radioactive thorium > but when confronted with the actual findings, finally admitted to it, along > with many more lens manufacturers, but the Leica pre-1M are the most > famous and command a premium price today even though the yellowish > brown tint of the lenses will discolor chrome films. > > Frau Doktor Mary Grace McGough > > In a message dated 1/27/00 2:28:04 PM Pacific Time, zeissler@wt.infi.net > writes: > > > > According to my wife [who does radioactive particle analysis for a living], > > distance would play a crucial role in whether the film was exposed or not > by > > the Thorium elements. According to her, the alpha particles would not > > expose film outside of a fairly short distance [~2 inches or less, > depending > > on some variables], while gamma particles would travel several yards.
From Leica Mailing List:
Date: Mon, 24 Jan 2000
From: Mike Johnston michaeljohnston@ameritech.net
Subject: [Leica] Radioactivity
Wouldn't a radioactive element in a lens cause film fog? Seems strange
that it should be purposely built in...
The earliest Super-Takumars for the Spotmatic had a radioactive element.
Roger Hicks says that if you let it sit for a while on a sheet of
Polaroid and then pull the Polaroid, you can see a faint shadow. I've
never tried it.
- --Mike
Date: Thu, 30 Dec 1999
From: dickburk@ix.netcom.com (Richard Knoppow)
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Glowing Lenses (radioactivity)
wicked007 version001NOveSPAM@hotmail.com wrote:
>I recently discovered that Kodak coated their AeroEktar lenses with >radioactive materials during the Second World War. Apparently you are >able to hold a geiger counter to the lenses and actually get a reading. >I was wondering if anyone knows of any other lenses that were coated >with harmful materials? Just curious. > >suspect007
Not from a coating. Some elements in the Aero Ektar are made with
Lanthanum glass. Early Lanthanum evidently contained some radioactive
isotopes of Lanthanum as an impurity, which made the glass itself
somewhat radioactive. Not a great deal of radiation. Lanthanum glass
has been used in a great many lenses designed after about 1940 but
most of it not radioactive.
About the only other radioactive glass used in lenses is Thorium
glass, which is quite definitely radioactive. I can't think of any
commercial lenses it was used in.
Radioactivity affects some optical glasses badly, causing them to
turn brown. The development of radiation resistant, non-browning
optical glass for use in defense or nuclear monitoring has been an
ongoing project of optical glass makers.
---
Richard Knoppow
Los Angeles, Ca.
dickburk@ix.netcom.com
Date: Wed, 29 Dec 1999
From: "Mark Bergman" mb50742@navix.net
Newsgroups: rec.photo.equipment.medium-format
Subject: Re: Glowing Lenses (radioactivity)
It's not just the older lens either. I have a Leica 35mm F2.0 Summicron
made in Canada and it is quite "hot". I made the mistake of taking the
camera & lens inside the power block at the Nuclear power plant where I
work to take some pictures. Being a newer lens I didn't have the Health
Physic Tech's check it before I took it in. Everything that comes out of
the power block gets scanned for radioactive contamination. The lens set
off the alarms. The assumption is then made that anything that is
contaminated got contaminated inside the power block and if can't be
cleaned it goes to the low level rad dump in SC with all the medical
waste. It took a lot of arguing to get the Tech's to do a complete
analysis of the lens and determine that it was the glass that was
radioactive and thus it wasn't contaminated, took about 3 months. I can't
remember the analysis but I believe the glass was thorium.
Most of the danger (which is either extremely little or none at all) in
this time of radiation is in the manufacture and the workers who deal with
it all day long.
From Rollei Mailing List:
Date: Fri, 24 Sep 1999
From: Bob Shell bob@bobshell.com
Subject: Re: [Rollei] Re: [Rollei] Off topic: Voigtlander Lanthar
BTW, I left something out of my post. Roger suggests that if you think
you have a "hot" lens, put it on top of a 4 X 5 sheet pack of Polaroid
3000 speed and leave it for a week. Then process the sheet and if the
lens is "hot" you'll see it clearly. Simple test for those who want to
know about a specific lens.
Bob
> Good enough. I have had a time keeping up with e-mail and Usenet the last > few days so I am late in responding. > I also read your later post about the impurities in the rare earths used > in optical glass. The presence of impurities could certainly explain > explain radioactivity in glass made with Lanthanum, which is not normally > radioactive. > ---- > Richard Knoppow > Los Angeles,Ca. > dickburk@ix.netcom.com
Date: Mon, 20 Sep 1999
From: Bob Shell bob@bobshell.com
Subject: Re: [Rollei] Off topic: Voigtlander Lanthar
I'm sure someone here knows the optical formula. I used to, but just
don't recall it at the moment. An interesting thing about the Lanthar
lenses is that the name comes from Lanthanium, a rare earth used to
make some of the special glass used in these lenses. Lanthanium is
radioactive and the Lanthar lenses are among those known as "hot"
lenses.
Roger Hicks tested some of these lenses last year by leaving them
on top of sheet film holders with ISO400 film in them. After a few
days he processed the film, and there was a nice fogged area where
the lens had been. There is not enough radiation to be concerned
with. Just don't sit around for a couple of days with one of these
lenses in your lap!!!
I would also assume that in a folding camera, storing the camera
for any length of time folded with film in it would fog the film
frame under the lens.
Bob
....
From Rollei Mailing List;
you wrote:
You mean he got fogging with the lens in its normal postion mounted on a
camera? Did he actually make any radiation tests using a counter? Lets
say
I remain skeptical.
There are an awful lot of lenses with lanthanum glass glass in them.
Lanthanum crown glasses were degeloped by Morey at the NBS in the mid
1930's and developed commercially by Kodak who produced several Lanthanum
glasses. They were applied to a wide variety of lenses by the 1940's
including the Ektar series of Tessar type lenses. There are likely few
lenses made in the last sixty years which do not contain some Lanthanum
glass. It was one of the first high index-low dispersion glasses.
Morey also worked with Thorium and other rare eaths, some of which are
slightly radioactive. Thorium was used in some aerial lenses, notably the
Aero-Ektar. Thorium glass tends to yellow with age and is not used
generally in lens making.
Thorium was also used (and may still be) in doping the tungsten filiment
wire used in radio transmitting tubes. Thoriated tungsten has much higher
emmission than plain tungsten. I think it is also used in some X-ray
applications.
Again, Lanthanum glass is used in practically every lens designed after
about 1946, when it became widely available so if it is radio active all
those lenses must be radioactive.
I do not have either the CRC handbook or Merck's index handy, either
should give authoritative data about radioactivity of elements.
----
Date: Wed, 22 Sep 1999
OK, my friend and colleague Roger Hicks knows more about lenses than
any four others I know combined. Here is what he says about this
question of "hot" lenses.
Bob
From: szekeres+@pitt.edu (greg s)
pburian@aol.com (PBurian) wrote:
It seems uncertain on how many passes it might take, on a carry on to
affect the film. Its uncertain circumstances which can create so-called
myths.
I was concerned about the radiation comming off my Pentax 1.4 50 SMC lens
with uranium substances on the coating, mostly the rear side, but I never
really had problems with film exposure. It must take a wallop to get it
recordable on the film, or extra high sensitivity. The company just said
not to wear the camera for long periods! Having high energy, the radiation
goes through allot more than just an alpha emitter. I originally located
my radioactive camera case while searching the house for any radiation.
Only that paticular lens though.
greg
From Rollei Mailing List:
I have a 50mm Nokton for a Voigtlander Prominent that has also turned a
yellow-brown color. I is a "hot" one, and i determined this by placing it
upon a sheet of Polaroid sheet film that was subequently developed to show
the fogging that resulted from the (mostly) alpha and beta decay from rare
earth elements used in formulating the optical glass. The advantage is, I
suppose, that the lens gives great sky contrast. No need for a yellow
filter.
----- Original Message -----
From Leica Mailing List:
If I recall correctly these/this article/s was taken from the
(British) LHS
magazine,
'LHS Newsletter', Issues 42 and 44,
'The Development of Leica F2 Standard Lenses Part II: 1945-Present', and
'Further Details on the Radioactive F2 Summicron Lens', both written by
Dr. Cyril T. Blood.
Jem
- -----Original Message-----
P.S. More seriously, there was an article about radioactive lens
components back in the 50's. It may have been in the LHSA magazine.
Does anyone remember?
[Ed. note: thanks to John Sonderegger and Todd Gustavson for providing
this useful health related
information!..]
I thought this information would be a useful addition to your page.
John
Yes, your 24-inch f/6 Aero Ektar lens, which was made in 1945, has a rear
element containing radioactive thorium. According to an article published
in the British Journal of Photography, March 20 and October 29, 1987, the
beta + gamma ray emissions from this lens are 850 counts per second, and
the gamma rays alone are 320 counts per second. There is, therefore, a
health risk associated with this lens. The original use for this lens was
in aerial cameras made for daylight reconnaisance on up to 9 x 18 inch
film. Presumably it would cover an area 18 x 18 inches, but since it is an
aerial lens it was calculated for extreme distances and may not have the
same resolution when used at shorter distances.
Sincerely,
Todd Gustavson
Date: Thu, 01 Feb 2001
Comment for the thread at:
Radioactive Glass in Lenses Are Your Lenses Really "Hot"?!!
The first (silver nosed) version of the Canon FD 35mm f/2 is hot - as
per testing on a Geiger counter. I did an SQF-style lens test of it (
see: http://members.aol.com/canonfdlenstests/default.htm ) and it is a
supurb performer, albeit with a significant green-yellow color cast
rendering it unsuitable for color slide photography.
Gary Reese
[Ed. note: for Guido Cova, and thanks to Steven for sharing this
info!]
Monday, May 28, 2001
Dear Guido,
I recently acquired a Praktica thread Pancolar lens, such as the one you
mentioned, and can affirm that at least one element has gone yellow, if
not yellow-greenish. I saw your contribution to the radiaoactive lenses
page on Robert Mognahan's site and wondered if you'd found any more info,
since no one replied to you on the page.
I'm trying to locate someone with a geiger counter, indeed to test other
lenses I own, for the presence of radioactive emissions. If I find
anything out, I'll be certain to let you know. Please let me know if you
find out anything.
Sincerely,
Steven Bailey abbailey1@earthlink.net
[Ed. note: thanks to Mr. Pete Andrews for sharing these observations and
warnings!]
Dear Sir.
Having just run both a geiger counter and a dosimeter over a 7" Aero
Ektar, I found that the rear element was extremely radioactive. More
worryingly, the emission was NOT relatively harmless alpha, but Gamma
particles. Interposing a 1" thick piece of perspex and a 3mm steel plate
had no effect on the geiger counter readings.
I did this test in the company of an expert in the field of radiological
protection, and he concurred that the emission was almost certainly
Gamma radiation.
I told him that the likely culprit was Thorium in the glass, and after
consulting some tables, he stated that the decay products of Thorium
were nearly all Gamma emitters, making the radiation extremely
energetic, and therefore quite hazardous.
"I wouldn't sit on that lens for any length of time!" was his comment.
The readings we got from the dosimeter in close contact with the lens
were higher than permitted for monitored radiation workers, and at 6"
from the lens the dose was still just over the limit for 'civilian'
exposure. A salutory finding.
My radiation savvy friend tells me that it takes about 6 years for
Thorium to decay to the point of producing any appreciable quantity of
gamma emitters. He reckons that after a further 9 years the process
should bottom out, and the gamma activity shouldn't continue to rise
after that time. The Aero Ektar is over 30 years old, so that point is
already well past.
Thorium has a half-life of 10 to the power of 10 years, so it ain't
gonna get noticeably less active either.
I think you ought to amend your web page, to warn about the potential
Gamma radiation hazard from Aero-Ektars, and maybe any other lenses that
use Thorium glass.
It's rumoured that some of the recent Kiev factory lenses are 'hot' as
well.
I have quite a collection of oddball lenses, so I'll test a few others,
but I don't have any containing Lanthanum glass, to the best of my
knowledge.
Keep a pair of lead-lined underpants spare for testing those old lenses.
;^)
Regards, Pete Andrews.
From Leica Mailing List;
Hugh Thompson wrote:
Off the top of my head, I recall that all of the affected lenses were
right around the 1,000,000 mark, most below. There is supposedly a yellow
cast in the glass of these guys.
Marc
From Leica Mailing List;
(Sent earlier as HTML-sorry)
Talking to a dealer this evening and he told me that glass in some 1950's
M lenses is radioactive, and the lenses have added value because of their
rarity.
I have real trouble believing this, but, if correct, what serial numbers
are we talking about?
Hugh Thompson - painfree@istar.ca
From Leica Mailing List;
Hugh Thompson writes:
Leica and most other manufacturers of good lenses use special glasses to
obtain the optical characteristics they require. At one time, Leica had
its own glass lab, and at least one of the glasses it produced contained
thorium oxide. Thorium is a mildly radioactive metal similar to uranium in
its radioactivity. The use of thorium and lanthanum oxides made it
possible to obtain very high indices of refraction with low dispersion,
which is useful for correction of many aberrations.
Unfortunately I can't be more specific on which lenses used
thorium-containing glasses; I only know (thanks again to Erwin Puts) that
a few lenses were designed with such glasses. These may only have been
the few that incorporated glass from Leica's own small glass lab. The
early Noctilux incorporated special glass from this lab, but I don't know
if it used a thorium-containing glass. In any case, that Noctilux is
extraordinarily rare today (and should not be confused with the current
Noctilux, which uses off-the-shelf optical glasses without thorium).
Thorium is not a health hazard unless you eat it or inhale it, and even
then, it presents only a tiny risk, compared to most radioactive isotopes.
It is still used for fabrication of specialty optical glass (but I don't
know if Leica ever uses it). It is also widely used for the mantles of
gas lamps, as an alloying ingredient with magnesium, in refractories for
crucibles and furnaces, and the like.
From Leica Mailing List:
Mxsmanic wrote:
The affected lenses were pre-production and very early production 2/5cm
collapsible Summicrons. See Dr Blood's article in VIEWFINDER four or five
years back.
Leica did, and still does, to my knowledge, have a laboratory for optical
glasses, but it has never made its own glass. Until 1926, it used glass
from CP Goerz in Berlin and then, after the Zeiss Ikon merger closed that
facility, shifted to Schott glass, first from Jena and, after the Second
World War, from Mainz. In recent years, some of the Schott glasses
supplied have come from Hoya, who manufactures them under license.
Marc
From Leica Mailing List;
Marc - thanks for taking the time to comment - Hugh Thompson
- ----- Original Message -----
Hugh Thompson wrote:
Off the top of my head, I recall that all of the affected lenses were
right around the 1,000,000 mark, most below. There is supposedly a yellow
cast in the glass of these guys.
Marc
Date: Mon, 25 Feb 2002
From: Richard Knoppow dickburk@ix.netcom.com
To: rollei@mejac.palo-alto.ca.us
Subject: RE: [Rollei] Re: My Retina died yesterday (RIP) --> glass with t
you wrote:
>Richard Knoppow dickburk@ix.netcom.com wrote:
>
>I have some additional comments to Richard's posting, and there is even an
>on-topic remark below on a Rollei TLR lens.
>
>I have been researching thorium-containing glasses and especially the Kodak
>Aero-Ektars. I have tried to rely on original literature and measurements
>because many of the secondary sources have errors. I have written up some of my
>findings: http://home.earthlink.net/~michaelbriggs/aeroektar/aeroektar.html
A belated thank you for posting this, it really is much more definite
than the info I've been able to pick up.
FWIW, the lens in the Aklin patent, USP 2343627, appears in _Modern Lens
Design: A resource manual_ Warren J. Smith, 1992, McGraw-Hill Book Co. ISBN
0-07-059178-4 on page 345. The precription is given with a schematic
diagram and an computer analysis of the lens performance.
Both of the high index elements are given as what I thought was a
Lanthanum glass number. These are the #5 and #6 elements counting from the
front #5 is given as LAF2 and #6 as LAF 24. I don't have a glass catalogue
to check this, perhaps these refer to Thorium glass but I thought LAF meant
lanthanum flint.
I will down load the actual patent at work (were I have a T-1 line) I
scanned it but don't remember if the glass types are described in any other
than Index and v number.
----
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com
From: handerle@klosterneuburg.net (Dr. Heinz Anderle)
Newsgroups: rec.photo.equipment.35mm
Subject: Vivitar 35 mm/1,9 - also a radioactive lens
Date: Sat, 02 Mar 2002
I have purchased a Vivitar 35 mm/1,9 high-speed wideangle recently and
wondered about the yellowish tint. I had visited Robert Monaghan's
page about radioactive lenses before and so I measured the
radioactivity with a Geiger counter - and voil.! ~ 3,8 Becquerel at a
distance of ~ 1 cm from the rear element.
It is nevertheless an excellent lens of the early 1970s - little
vignetting and no distortion (you can't stop down the latter, even if
you have the expensive Nikkor 35 mm/1,4...). And it doesn't fog Neopan
1600.
I still wonder why lens design has rather deteriorated than improved
since then - at least for today's consumer grade lenses.
Dr. Heinz Anderle ("High-Mech" traditionalist - autofocus doesn't work
without batteries)
From: "jriegle" jriegle@att.net
Newsgroups: rec.photo.equipment.35mm
Subject: Radioactive lenses
Date: Tue, 19 Feb 2002
The discussion about radioactive materials used in glass was interesting...
I had to experiment for myself.
http://home.att.net/~jriegle/radioactive.htm
John
Date: Wed, 13 Feb 2002
From: Michael Briggs MichaelBriggs@earthlink.net
To: rollei@mejac.palo-alto.ca.us
Subject: RE: [Rollei] Re: My Retina died yesterday (RIP) --> glass with t
Richard Knoppow dickburk@ix.netcom.com wrote:
I have some additional comments to Richard's posting, and there is even an
on-topic remark below on a Rollei TLR lens.
I have been researching thorium-containing glasses and especially the Kodak
Aero-Ektars. I have tried to rely on original literature and measurements
because many of the secondary sources have errors. I have written up some of my
findings: http://home.earthlink.net/~michaelbriggs/aeroektar/aeroektar.html
> Kodak took on the commercial development of the rare earth glasses
> resulting from research at the National Bureau of Standards. The glass
> research was done in the early to mid thirties and Kodak began to
> manufacture and employ the glass in the late 1930's. Its hard to determine
> exact dates but from the evidence of some of the lenses it seems possible
> that at least some Lanthanum glass was employed as early as 1935.
The probable date for first production use is probably a bit later than 1935,
perhaps as late as 1939. Kingslake (Nature, 163, 412-413, 1949) says "The
new glasses were first used in lens design in 1934; the actual production of
the lenses began a few years later, and today many of the Eastman Kodak Ektar
lenses contain the high-index glass." However, I think that the patent
closest to the glasses that Kodak put into production is Eberlin and De
Paolis, US 2,241,249, applied for in 1939. The first patent (Morey) was
originally filed in 1936 but reissued in 1939 as Re. 21,175. (Does anyone
know the meaning of a reissue patent? Was there a problem with the original?)
The Aero-Ektar may be one of the first lenses to use the new glasses--this
patent was applied for in 1941 (Aklin, 2,343,627).
> Lanthanum glasses are the most widely used of the rare-earth glasses but
> there were some others. Thorium glass was evidently employed in some aerial
> lenses, but Thorium glass is quite radioactive. Enough to be a hazard plus
> the radioactivity tends to turn the glass brown in a relatively short time.
In the 1940/1950 period, I haven't found use of the term "Lanthanum glass.
Many terms were used, such as Kodak special glass, borate glass, non-silicate
glass, .... The term "lanthanum glass" applied to the early glass is somewhat
misleading since these glasses could just as easily been called borate glass or
thorium glass: AFAIK, all the production glasses included at least these three
elements. In his 1949 Nature paper, Kingslake states that all the special
glasses made by Kodak include thorium.
I would term Thorium glass "definitely" radioactive. Possession by ordinary
people (those without a radiation license) is legal in the US. My view (which
I don't guarantee) is that thorium containing lenses are reasonably safe but
shouldn't be stored close to people.
> ... turn the glass brown in a relatively short time.
This depends on your definition of short. Many people don't notice the brown
color of the Aero-Ektars today, more than 50 years after their production. The
Once you know how to look for it, the brown is quite noticeable. In a smaller
lens with thinner elements, it would probably not be so noticeable. Even in
the Aero-Ektars, it might have been 20 years before the brown became
noticeable, partly because not as much browning would have occurred in the first
few years because the radiation level would have been less before the daughter
isotopes built up.
> Since the lenses employing it were made for war time use their immediate
> performance was much more important than long life; essentially they were
> considered expendibles.
I agree that the goal of the Aero-Ektars was winning WWII and the relevant
people wouldn't have cared if they knew the lenses would self-destruct after
the war. However, I don't think they knew that the lenses would ever
self-destruct. My guess is that radiation browning of glass was probably
discovered by the Manhattan Project or from early reactors. If so, this
problem wouldn't have been known by ordinary scientists until the 1950's.
The only concern that I have seen expressed in period literature is Kingslake's
statement "All of these glasses contain thorium, and in the case of folding
cameras, in which the lens may rest for a long time in close proximity to film,
the radioactivity of the thorium may be a disadvantage." In literature from
the 1940s and 1950s, I have never seen any concern with browning or with
safety,
either of the user or in manufacturing (which could be much more dangerous from
breathing airborne dust).
> I have no information as to which specific lenses used Thorium glass.
There are extensive lists in two articles in the British Journal of
Photography, both by Frydman and Wright: on 20 March 1987 and 29 October
1987. Radioactive lenses are listed from virtually every lens manufacturer.
They don't list which lenses they tested and weren't radioactive, so the
absence of a manufacturer doesn't mean that they didn't make radioactive
lenses. Some of the manufacturers are Kodak, Canon, Jena, Voigtlander,
Schneider, and Asahi. This is even on-topic: they list "Schneider/Rollei" for a
75 mm f3.5 Xenotar on a 6x6 TLR--no details of the model are given. The
radiation level on the Rollei is much lower than for most of the other
examples.
My guess is that there are probably far more radioactive lenses out there, made
in the 1940s, 1950s and 1960 and perhaps the 1970s, then most photographers
realize. The hazard is low, but I suggest not storing older lenses in close
proximity to yourself. A few meters will make a big difference.
Personally, I am not worried about using camera lenses that might be
radioactive. Right now I am concentrating my research efforts on the
Aero-Ektars, but I will probably expand my study to other lenses--I might start
taking measurements of lenses in people's collections.
The easiest way for a photographer to test a lens for radioactivity is to make
an exposure on film. I used 4x5 filmholders. For a 7 inch Aero-Ektar, a two
week exposure on Delta 400 resulted in a base+fog density of 0.39 above normal
and a spot in the center with a peak density of 0.79. This is from 10 min
development in D-19 with constant rotary agitation at 66 deg F. Both the front
and rear ends should be tested because the radiation levels can be quite
different. Because of their size, the Aero-Ektars have higher radiation levels
then most other lenses with thorium content, however, the Aero-Ektars
self-shield since the thorium containing elements are internal, so a small lens
might have a higher than expected radiation level if it had an external thorium
containing element.
> Lanthanum glass has the advantage of having a relatively high average
> index of refraction and relatively low dispersion, which is the variation of
> index with wavelength. The high index results in less curved surfaces for a
> given amount of power, which in turn results in reducing the aberrations.
> The low dispersion means that color aberrations become easier to correct.
> Some aberrations (astigmatism is one of them) depend for their correction
> on the ratio of the index of refraction of the various elements,
> particularly positive vs: negative elements. Since dispersion tends to
> increase with index there were limits on the ratio of indexes which could
> be used and still have good chromatic correction. The availability of,
> especially, the Lanthanum series allowed much better correction of
> aberrations than was previously possible.
This is a good explanation of the advantages of these glasses.
> Rare earth glasses are not easy to make. They must be melted in pure
> platinum pots and at rather high temperatures.
The platinum pots were one of the Kodak innovations.
If any of you own an Aero-Ektar, I would like to receive off-list the rim data,
and especially the serial number. I am trying to estimate production years
and volume.
--Michael
[Ed. note: no guarantees, but this is interesting enough to pass and try?...]
From: "jriegle" jriegle@att.net
Newsgroups: rec.photo.equipment.35mm
Subject: Radioactive lenses - getting the yellow out
Date: Tue, 12 Mar 2002
If you own an older lens that had those infamous radioactive elements that
turned yellow with age such as some of the old Takumar 50s, Leica Summacrons
or others, don't despair, try this trick. I set my old SMC Takumar 50mm
1:1.4 lens in a sunny windowsill for two weeks and the sun has bleached
almost all of the yellow out! No more color shifts!
I can't tell you if it will work for other types of lenses but it is worth a
try! I set the lens so the yellowed rear element was towards the light and
kept the front cap on to avoid the sun getting focussed on something and
starting a fire : )
No I didn't use a popcorn popper for those who remember my last radioactive
lens post ; )
You can read more about radioactive lenses here
http://medfmt.8k.com/mf/radioactive.html
John
Date: Tue, 26 Feb 2002
From: Richard Knoppow dickburk@ix.netcom.com
To: rollei@mejac.palo-alto.ca.us
Subject: RE: [Rollei] Re: My Retina died yesterday (RIP) --> glass with t
you wrote:
>Richard Knoppow
Date: Thu, 19 Apr 2001
From: Virginia Koukouliou vkoukoul@eeae.nrcps.ariadne-t.gr
To: rmonagha@post.cis.smu.edu
Subject: Thorium lens
GREEK ATOMIC ENERGY COMMISSION
DEPARTMENT OF ENVIRONMENTAL RADIOACTIVITY
Dr. Virginia Koukouliou
Tel : ++ 30 1 6506777
Fax: ++ 30 1 6506748
Dear Mr. R.Monaghan,
Recently a lenses collector asked us to measure a Rodenstock
XR-Helingon 1:0,75 50mm lens. We found thorium in a quantity
of above 10000 Bq. This quantity exceeds the excemption levels for
thorium according to the 96/29 Euratom Directive. The total beta and
gamma dose at the surface is up to 20 microSv/h.
We have been informed that the lens was possibly a component of an X-ray
machine (propably a mammography unit ?). We would very much appreciate
if you could give us any information (use, generation) concerning this
type of lens. Is there any regulation concerning the ammount of thorium
concentration in lenses ?
Thanking you in advance for your collaboration, I remain
Sincerely yours
V. Koukouliou
Date: Sun, 22 Apr 2001
From: Virginia Koukouliou vkoukoul@eeae.nrcps.ariadne-t.gr
To: Robert Monaghan rmonagha@post.cis.smu.edu
Subject: Re: Thorium lens
Dear Mr. R. Monaghan,
Thank you very much for your mail. There is no problem to inform other owners of
similar lenses that these type of lenses may
exceed the current EU radioactivity limits. It could be a good idea to examine
them. They must be used carefully and not as a telescope eye-piece. Maybe the new
version of Rodenstock XR-Helingon 1:0,75 50mm lens does not exceed today's more
conservative radioactivity standards. Please attach this mail to the first one,
before put it at your web page.
Best regards
Virginia
From: handerle@klosterneuburg.net (Dr. Heinz Anderle)
Newsgroups: rec.photo.equipment.35mm
Subject: Re: Radioactive lenses - getting the yellow out
Date: Tue, 12 Mar 2002
"jriegle" jriegle@att.net
>If you own an older lens that had those infamous radioactive elements that
>turned yellow with age such as some of the old Takumar 50s, Leica Summacrons
>or others, don't despair, try this trick. I set my old SMC Takumar 50mm
>1:1.4 lens in a sunny windowsill for two weeks and the sun has bleached
>almost all of the yellow out! No more color shifts!
>
>I can't tell you if it will work for other types of lenses but it is worth a
>try! I set the lens so the yellowed rear element was towards the light and
>kept the front cap on to avoid the sun getting focussed on something and
>starting a fire : )
>
>You can read more about radioactive lenses here
>http://medfmt.8k.com/mf/radioactive.html
>
>John
>
Good idea, some crystal lattice defects can be bleached with light.
(During my work for my Ph. D. Thesis, I had mussel shells irradiated
in marmalade jars, which turned deep-brown and subsequently were
bleached by ambient light.)
I will try this for my Vivitar lens as well.
Dr. Heinz Anderle
From Rollei Mailing list:
Date: Sun, 03 Feb 2002
From: Richard Knoppow dickburk@ix.netcom.com
Subject: Re: [Rollei] Re: My Retina died yesterday (RIP)
you wrote:
>Richard Knoppow wrote:
>
>> The 47mm, f/2.0 is a six element Planar (or rather Biotar) type. The one
>> for the Bantam Special was the very first lens to bear the name Ektar.
>> Kodak also made a seven element 50mm, f/1.9 Planar type for the Ektra camera.
>> The Ektra had a couple of interesting lenses made for it. The 35mm, f/3.3
>> Ektar is a Heliar type, one of the series Altman designed.
>> The Bantam Special Ektar, the Ektra lenses, and the early Medalist lenses
>> were all soft coated on internal surfaces.
>> The Ektra was not successful probably because it was released too close
>> to the outbreak of WW-2, but it also had some ergonomic problems and got a
>> reputation for shutter problems.
>> I wonder of any Rollei types have working Ektra cameras?
>
>
>I have the block diagram for the 50/1.9 but unfortunately not the f/2... the
>former is of the same construction as the original Summicron except the
>first two groups are cemented and not air spaced...
>
>What's missing from these discussions is the widely held acknowledgement
>that Kodak's build quality for these premium lenses was second to none...
>their Tessar-based lenses are spectacular performers with generous use of
>so-called "rare earth" glass and very high levels of quality control...
>years ago I've saw secondary spectrum curves from when these lenses were
>introduced and they were very close to apochromatic. I have seen chromes
>from the 6-element ektar-based Retinas as a pal of mine had one and remember
>being just stunned by the beautiful character of the images... when that
>camera wound up at the bottom of a lake, tears literally came to my eyes...
>
>Have never seen an Ektra image... Richard, my internet pal Bob Howard had
>one as the original owner and always claimed the lenses were tremendous but
>the ergonomics were horrendous! He passed away a few years ago and I do not
>know what his daughter did with this set... local collecting legend Jack
>Naylor (who I just saw today) has an Ektra but to my knowledge has never put
>film through the camera and it may not be operational...
>
>Kodak lenses of this ilk were among the best money could buy and still hold
>up beautifully today...
>
>
>Eric Goldstein
The following appears in the description section of the 1948 edition of
the Kodak lens booklet included in the _Kodak Reference Handbook_.
"Color correction has been carried out to such a degree that color
pictures made with Ektar lenses not only satisfy the demands of the most
critical color workers, but meet the far stricter requirments encountered
in photomechanical color reproduction."
The lenses must be nearly apochromatic.
Kodak took on the commercial development of the rare earth glasses
resulting from research at the National Bureau of Standards. The glass
research was done in the early to mid thirties and Kodak began to
manufacture and employ the glass in the late 1930's. Its hard to determine
exact dates but from the evidence of some of the lenses it seems possible
that at least some Lanthanum glass was employed as early as 1935.
Lanthanum glasses are the most widely used of the rare-earth glasses but
there were some others. Thorium glass was evidently employed in some aerial
lenses, but Thorium glass is quite radioactive. Enough to be a hazard plus
the radioactivity tends to turn the glass brown in a relatively short time.
Since the lenses employing it were made for war time use their immediate
performance was much more important than long life; essentially they were
considered expendibles.
I have no information as to which specific lenses used Thorium glass.
Lanthanum glass has the advantage of having a relatively high average
index of refraction and relativly low dispersion, which is the variation of
index with wavelength. The high index results in less curved surfaces for a
given amount of power, which in turn results in reducing the aberrations.
The low dispersion means that color aberrations become easier to correct.
Some aberrations (astigmatism is one of them) depend for their correction
on the ratio of the idex of refraction of the various elements,
particularly positive vs: negative elements. Since dispersion tends to
increase with index there were limits on the ratio of indexes which could
be used and still have good chromatic correction. The availablity of,
especially, the Lanthanum series allowed much better correction of
aberrations than was previously possible.
Rare earth glasses are not easy to make. They must be melted in pure
platinum pots and at rather high temperatures. Beside their inherent
properties they must also meet the general requirements for good optical
glass, namely freedom from striations or other turbidity, lack of bubbles
or voids, freedom from stains, general cleanliness, and chemical stability.
It makes optical glass expensive and rare-earth types particularly expensive.
I am another who thinks Kodak was probably making the best lenses in the
world during the period Rudolf Kingslake was running their optical
department.
----
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com
Date: Wed, 13 Feb 2002
From: Michael Briggs MichaelBriggs@earthlink.net
To: rollei@mejac.palo-alto.ca.us
Subject: RE: [Rollei] Re: My Retina died yesterday (RIP) --> glass with t
Richard Knoppow dickburk@ix.netcom.com wrote:
I have some additional comments to Richard's posting, and there is even an
on-topic remark below on a Rollei TLR lens.
I have been researching thorium-containing glasses and especially the Kodak
Aero-Ektars. I have tried to rely on original literature and measurements
because many of the secondary sources have errors. I have written up some of my
findings:
http://home.earthlink.net/~michaelbriggs/aeroektar/aeroektar.html
> Kodak took on the commercial development of the rare earth glasses
> resulting from research at the National Bureau of Standards. The glass
> research was done in the early to mid thirties and Kodak began to
> manufacture and employ the glass in the late 1930's. Its hard to determine
> exact dates but from the evidence of some of the lenses it seems possible
> that at least some Lanthanum glass was employed as early as 1935.
The probable date for first production use is probably a bit later than 1935,
perhaps as late as 1939. Kingslake (Nature, 163, 412-413, 1949) says "The
new glasses were first used in lens design in 1934; the actual production of
the lenses began a few years later, and today many of the Eastman Kodak Ektar
lenses contain the high-index glass." However, I think that the patent
closest to the glasses that Kodak put into production is Eberlin and De
Paolis, US 2,241,249, applied for in 1939. The first patent (Morey) was
originally filed in 1936 but reissued in 1939 as Re. 21,175. (Does anyone
know the meaning of a reissue patent? Was there a problem with the original?)
The Aero-Ektar may be one of the first lenses to use the new glasses--this
patent was applied for in 1941 (Aklin, 2,343,627).
> Lanthanum glasses are the most widely used of the rare-earth glasses but
> there were some others. Thorium glass was evidently employed in some aerial
> lenses, but Thorium glass is quite radioactive. Enough to be a hazard plus
> the radioactivity tends to turn the glass brown in a relatively short time.
In the 1940/1950 period, I haven't found use of the term "Lanthanum glass.
Many terms were used, such as Kodak special glass, borate glass, non-silicate
glass, .... The term "lanthanum glass" applied to the early glass is somewhat
misleading since these glasses could just as easily been called borate glass or
thorium glass: AFAIK, all the production glasses included at least these three
elements. In his 1949 Nature paper, Kingslake states that all the special
glasses made by Kodak include thorium.
I would term Thorium glass "definitely" radioactive. Possession by ordinary
people (those without a radiation license) is legal in the US. My view (which
I don't guarantee) is that thorium containing lenses are reasonably safe but
shouldn't be stored close to people.
> ... turn the glass brown in a relatively short time.
This depends on your definition of short. Many people don't notice the brown
color of the Aero-Ektars today, more than 50 years after their production. The
Once you know how to look for it, the brown is quite noticeable. In a smaller
lens with thinner elements, it would probably not be so noticeable. Even in
the Aero-Ektars, it might have been 20 years before the brown became
noticeable, partly because not as much browning would have occurred in the first
few years because the radiation level would have been less before the daughter
isotopes built up.
> Since the lenses employing it were made for war time use their immediate
> performance was much more important than long life; essentially they were
> considered expendibles.
I agree that the goal of the Aero-Ektars was winning WWII and the relevant
people wouldn't have cared if they knew the lenses would self-destruct after
the war. However, I don't think they knew that the lenses would ever
self-destruct. My guess is that radiation browning of glass was probably
discovered by the Manhattan Project or from early reactors. If so, this
problem wouldn't have been known by ordinary scientists until the 1950's.
The only concern that I have seen expressed in period literature is Kingslake's
statement "All of these glasses contain thorium, and in the case of folding
cameras, in which the lens may rest for a long time in close proximity to film,
the radioactivity of the thorium may be a disadvantage." In literature from
the 1940s and 1950s, I have never seen any concern with browning or with safety,
either of the user or in manufacturing (which could be much more dangerous from
breathing airborne dust).
> I have no information as to which specific lenses used Thorium glass.
There are extensive lists in two articles in the British Journal of
Photography, both by Frydman and Wright: on 20 March 1987 and 29 October
1987. Radioactive lenses are listed from virtually every lens manufacturer.
They don't list which lenses they tested and weren't radioactive, so the
absence of a manufacturer doesn't mean that they didn't make radioactive
lenses. Some of the manufacturers are Kodak, Canon, Jena, Voigtlander,
Schneider, and Asahi. This is even on-topic: they list "Schneider/Rollei" for a
75 mm f3.5 Xenotar on a 6x6 TLR--no details of the model are given. The
radiation level on the Rollei is much lower than for most of the other
examples.
My guess is that there are probably far more radioactive lenses out there, made
in the 1940s, 1950s and 1960 and perhaps the 1970s, then most photographers
realize. The hazard is low, but I suggest not storing older lenses in close
proximity to yourself. A few meters will make a big difference.
Personally, I am not worried about using camera lenses that might be
radioactive. Right now I am concentrating my research efforts on the
Aero-Ektars, but I will probably expand my study to other lenses--I might start
taking measurements of lenses in people's collections.
The easiest way for a photographer to test a lens for radioactivity is to make
an exposure on film. I used 4x5 filmholders. For a 7 inch Aero-Ektar, a two
week exposure on Delta 400 resulted in a base+fog density of 0.39 above normal
and a spot in the center with a peak density of 0.79. This is from 10 min
development in D-19 with constant rotary agitation at 66 deg F. Both the front
and rear ends should be tested because the radiation levels can be quite
different. Because of their size, the Aero-Ektars have higher radiation levels
then most other lenses with thorium content, however, the Aero-Ektars
self-shield since the thorium containing elements are internal, so a small lens
might have a higher than expected radiation level if it had an external thorium
containing element.
> Lanthanum glass has the advantage of having a relatively high average
> index of refraction and relatively low dispersion, which is the variation of
> index with wavelength. The high index results in less curved surfaces for a
> given amount of power, which in turn results in reducing the aberrations.
> The low dispersion means that color aberrations become easier to correct.
> Some aberrations (astigmatism is one of them) depend for their correction
> on the ratio of the index of refraction of the various elements,
> particularly positive vs: negative elements. Since dispersion tends to
> increase with index there were limits on the ratio of indexes which could
> be used and still have good chromatic correction. The availability of,
> especially, the Lanthanum series allowed much better correction of
> aberrations than was previously possible.
This is a good explanation of the advantages of these glasses.
> Rare earth glasses are not easy to make. They must be melted in pure
> platinum pots and at rather high temperatures.
The platinum pots were one of the Kodak innovations.
If any of you own an Aero-Ektar, I would like to receive off-list the rim data,
and especially the serial number. I am trying to estimate production years
and volume.
--Michael
From Rollei Mailing List:
Date: Tue, 26 Feb 2002
From: Jerry Lehrer jerryleh@pacbell.net
Subject: Re: [Rollei] Re: My Retina died yesterday (RIP) --> glass with t
Richard
I recently checked a friends 7inch Aero-Ektar for the
"browning" phenomenon. It's really a light tan. He says
that it does not affect B&W; pictures very much, and it
is well within the color correction capabilities of most
machines which print from color negatives.
He uses that lens on a custom mount for a Visoflex III.
Very shortly, I hope to try it on my Leica CL. All I need
is the release arm for it.
Jerry
From camera makers mailing list:
From: SOEL96@aol.com
Date: Wed, 1 May 2002
Subject: Re: [Cameramakers] guesses...
To: cameramakers@rosebud.opusis.com
hi!
I saw a program on PBS eons ago (or maybe it was scientific american?) about
the darkening you have with your lenses-- the phenomenon is called, 'Photonic
Impaction', and apparently can be reversed by sending light in the opposite
way that it had before, dislodging the photonic sludge... I could be
dreaming, but it is worth checking out. (i browsed on a google.com search,
but couldn't find anything..)
good luck!
joel
From: "jriegle" jriegle@att.net
Newsgroups: rec.photo.equipment.35mm
Subject: Re: Old Pentax Spotmatic users out there?
Date: Mon, 06 May 2002
> 3: With regard to the lens, I would recommend that you pick up a
> SMC_Takumar 50mm f/1.4 normal lens on eBay. Be sure to get the newer
> version, with the rubber focusing ring, as the older version (with the metal
> focusing ring) had a problem with the multi-coating turning yellow over
> time.
This is not quite correct. It was the glass in the rear element. It had
traces of a radioactive element that caused the glass to yellow over time.
Follow this link to find out more:
http://home.att.net/~jriegle/radioactive.htm
Click on the link on that page
for tons of information on 'radioactive' lenses. Interesting stuff!
Also, don't avoid that yellowed optic. I set the lens in a sunny window for
about a month and the light completely bleached the yellow out of the lens.
It is now perfectly clear.
John
[Ed. note: thanks to Robert Mueller for these notes on clarifying sundry issues in this debate...]
Date: Wed, 08 May 2002
From: Robert Mueller r.mueller@fz-juelich.de
To: rmonagha@post.cis.smu.edu
Subject: Lanthanum. Thorium and radioactive glass
After reading a bunch of the above contributions I thought it would be well
to inject a few extra words on the subject.
1) The yellowing of glass such as seen in the Aero Ektars is much more
likely to be caused by a kind of radiation damage than by a change in the
amount of the radioactive element(s). Radiation produces so-called color
centers in many substances. Often these can be healed by warming the
material but whether this works with these lenses is an open
question (Does the necessary temperature damage the lens? Is it worth the
effort to remove the element and anneal it? Can it even be healed by this
method?) Sorry; I have no answers.
2) Quoting a dose in rems while ignoring distance is a rather loose
concept. Exposure falls rapidly with distance (far enough away the law is
1/(distance squared) but close to the lens this will not be valid.) How
many rems depends on the strength of the source and how far away it
is. Often we get no help on this critical factor in the above.
3) Several contributions mention use the prefix M to mean "milli". This
is a widespread misuse. Computer persons are among the worst for mixing
the capital and lower case M (m) and one finds such nonsense as mB to mean
megabyte, whereas it means 1/1000 byte (125 millibytes=1 bit). Likewise
1Mrem is 1 million rems, a rather bad dose. Of course, one can guess the
intended meaning, but should that be required? Now and then it is
impossible to guess with any certainty and better is to just learn the
correct, international convention and then follow it!
4) Lanthanum (not lanthanium) is indeed slightly radioactive but it decays
by electron capture or beta emission, with a very long half-life of 0.347
x 10E19, and only one isotope with an abundance less than 0.1 % occurs in
natural lanthanum. That is hardly threatening. Thorium is something else
because all isotopes are radioactive and it emits a large array of alphas,
which make a lot of radiation damage, but most of which will never leave
the glass (but might make a nice yellow tint after enough time!) Those
that do exit will not travel far, though they might make it to a film for a
6 inch lens. I believe they will not reach the film with a 12 inch Ektar
even if it is the back element having thorium when the lens distance is
positioned for focus of an object at infinity (of course,a collapsed camera
can bring the film nearer the lens, and that is a different story.) I
can't find a table of range versus energy for alphas at this moment so I
leave the question open about whether the more energetic alphas do reach
the film with the 6 inch Ektar, especially because one must also know the
distance from film to back element when the image is focused.
Both thorium and its daughters generate gammas, and these will escape
the glass. Few of them will contribute to darkening of film (they go right
through!). They do add some hazard to the user because you don't want to
go through the precautions needed to get rid of them. Again, distance does
wonders. As many have said, don't sleep with one of these lenses.
5) It is possible the radioactive elements in older lenses are an
"accident". Rare earths are hard to purify and so some radioactive stuff
might be in the lens although it is not essential to the glass
properties. As best I can determine, the thorium was introduced
deliberately for its valuable contribution to the glass
characteristics. In a lanthanum glass it might be there accidentally and
so the amount might vary widely in otherwise identical lenses, thus
explaining some of the differences mentioned above. Newer lenses could be
showing the improvements coming from improved refining methods for the rare
earths.
Little of what I have written is new to this discussion but I have some
hope to stamp out a couple false interpretations which have appeared long
after the correct ones were introduced into the discussion! Maybe
repetition will help. I apologize for boring those who have been getting
it right all along!
Bob Mueller
From camera-fix mailing list:
Date: Fri, 14 Jun 2002
From: Michael Briggs michaelbriggs@earthlink.net
Subject: RE: Yellow Nikkor 35/1.4
The issue is whether the lens looks yellow (probably amber) when the coating is
viewed in reflected light, or whether it looks amber when viewing through the
lens. If the "yellow" is seen in reflection, than it is probably the lens
coating. Nikon used such a coating for some years in the 1960s. If the
amber color is seen in transmission, then it might be from self-induced
radiation damage in thorium containing glass.
The discoloration of the thorium glass is a bulk property of the glass, so
thicker sections will appear darker. The thorium containing glass was the
first glass with a high-index of refraction and an extra-low dispersion.
(Today, there are non-thorium containing glasses with such properties, which
Nikon calls ED glass.) With these optical properties, the glass would normally
be used in convergent elements--these are convex and so thicker in the center.
Seeing an amber color looking through the lens and with the amber color being
darker at the center is strongly suggestive of thorium containing glass.
See more comments below.
> Date: Thu, 13 Jun 2002
> From: "dennycywong" dennycywong@yahoo.com
> Subject: Re: Yellow Nikkor 35/1.4
.............
> I have seen quite a few older Nikon lenses with yellow coating. That
> goes with the single coating technology available in the 1960s. The
> German optics had yellow plus purple color coating from that period.
> My guess it has more to do with the coating than the choice of glass.
>
> -Gene Poon
>
> Date: Wed, 12 Jun 2002
> From: Steven Bailey stiltonkopf@yahoo.com
> Subject: Re: Re: Yellow Nikkor 35/1.4
>
>
> Dear Kelvin,
> I'd like to back up Denny's contribution. I once owned a Photomic Nikon with
> a
> matching 50/1.4 and 105/2.5 Nikkor. The lenses had a yellowish (amber)
> coating
> on the front much as you describe your 35/1.4. I also owned at the same time
> an
> Exakta with an early 50/2 Pancolar - also a yellowish coating.
> All three of these lenses rendered superior colors on slide and print film.
> If you're noticing a serious yellow cast when viewing on-camera (compare with
> another lens looking at a well-lit white object), although it would be odd to
> suspect a Nikkor of having unstable radioactive elements in the glass I would
> see what film yields.
Articles in the British Journal of Photography show that most lens
manufacturers have used the thorium glass. A Nikon company webpages relates
that Nikon participated in the Japanese effort to develop thorium containing
glass. I don't have proof that Nikon used such glass, would not not find it
surprising.
> I have yet to try out my 50/1.8 Pancolars (early zebra
> M42 mount) but suspect I will see something unusual due to their heavy
> yellow/green cast. (Incidentally, their coating is purplish!) I have
> disassembled those lenses and found at least two glass element
> s (identical ones) which have gone totally yellow.
Many lenses with thorium containing glass used the glass in interior elements.
The exterior glass elements and the body of the lens shield away a
significant fraction of the radiation. If you disassemble the lens to reach
the thorium-containing elements, you will expose a substantially higher level of
radiation--probably not dangerous, but one might as well keep ones exposure to
a short time.
--Michael
P.S. I have a webpage with some of my findings on thorium containing glass and
the first lenses to use this glass, the Aero-Ektars:
http://home.earthlink.net/~michaelbriggs/aeroektar/aeroektar.html
From zeiss interest group mailing list:
Date: Thu, 13 Jun 2002
From: "John A. Lind" jlind@spitfire.net
Subject: Re: Discolored lenses
Bill wrote:
>But right now I'd like you to read and comment on something
>just posted, on the subject of thorium content in lenses, and
>some discoloration purportedly resulting therefrom. I feel that
>this is a subject worthy of considerable discussion here in
>zicg, amongst some of our highly scientifically-oriented
>members. There has recently been some slight allusion to
>the constitution of the 'newly recomputed Tessar', and the
>use of lanthanum and thorium, and I feel that this is a
>subject worthy or more than casual attention.
>
>Any comments?
Yes . . .
The discontinued 55mm f/1.2 Zuiko for the Olympus OM system (not the
current 50/1.2) used very slightly radioactive heavy earth elements (along
the lines of what you mentioned) in the glass formulation for at least a
large portion of their production. The purpose of using these materials
was achieving specific transmission qualities and refractive indices. It
has long been known the examples that used heavy earth elements in their
glass have visibly "yellowed" slightly over the years (measure this in
decades).
The discoloration has a minor effect on color images, but nothing very
objectionable, at least to those who use them. OTOH, there are those who
panic at the thought of radioactive glass in their lenses. The radiation
level, while measurably higher than background, is well within exposure
limits in normal use, even by active professionals (e.g. not having the
lens embedded in one's forehead to satisfy some inexplicable "Argus" fetish).
The Olympus OM 55/1.2 Zuiko dates to the very early 1970's and Olympus
wasn't the only company to use these types of glass formulations. There
are numerous other lenses dating to the late 1960's and early 1970's made
by other manufacturers that also have slightly radioactive heavy earth
elements in the glass.
That's my take on it . . .
-- John
From: Gregory Walker gwalker@jump.net
Subject: Re: Radioactive Material
Newsgroups: alt.war.nuclear
Date: Sat, 15 Jun 2002
bob wrote:
>>In the U.S.A. it is illegal to own ANY amount of plutonium.
>
> since when ?!?!?!?
> last time i checked there was a generic general lisence exemption
> applied to radioactive materials with an activity of under either 1 or 5
> ucuries,[snip]... this applies to ANY radioactive
> material, even fissile material...
What exactly did you check? The Atomic Energy Act and subsequent Nuclear
Regulatory Commission rules make a distinction between source material,
special nuclear material (SNM) which basically is fissile material, and
byproduct material. The definition of these three types of material can
be found at this DOE web site:
http://tis.eh.doe.gov/oepa/law_sum/AEA.HTM
The full NRC regulations can be found here:
http://www.nrc.gov/reading-rm/doc-collections/cfr/
The text makes for endlessly convoluted reading, but lets cut to the
chase. This section states that a license is required for any special
nuclear material:
http://www.nrc.gov/reading-rm/doc-collections/cfr/part070/part070-0003.html
The exempt quantities of byproduct material you refer to are in fact
different depending on the particular isotope. They are defined in
this table:
http://www.nrc.gov/reading-rm/doc-collections/cfr/part030/part030-0071.html
You know, I love the web. Thirty minutes searching with Google and I was
able to find all those details.
Cheers,
Gregory Walker gwalker@jump.net
Trinity Atomic Web Site --
http://www.cddc.vt.edu/host/atomic/
http://nuketesting.enviroweb.org/
From russian camera mailing list:
Date: Mon, 12 Aug 2002
From: "Jay Y Javier" nikitakat@edsamail.com.ph
To: russiancamera-user@beststuff.com
Subject: Re: [Russiancamera] What is lantan technology ?
For Q1 and Q3:
Lantan (like the "L" in I-61 L?) is lanthanum added to the glass formula used
in the lens element(s).
The White Window on the M-Leicas (also found on the IIIg, and several later
Canon RF and Nikon RF) is the frame illumination window. It illuminates the
floating frames found in the viewfinder.
Jay
russiancamera-user@beststuff.com wrote:
>Can any one tell me what is :
>1. Lantan technology in making lens?
>2. What is a enlightener lens?
>3. Off topic, what is the white window next to the viewfinder on a Leica M
>series cameras?
From camera fix mailing list:
Date: Wed, 18 Sep 2002
From: John Barlow BARLOWJG@CHHA.CO.UK
Subject: RE: Yellowed Takumar 50mm f1.4 cure
The best info I have found on replacing the balsam cement in lenses is on
the S K Grimes site @ www.skgrimes.com
The description is for large format lenses but I expect it is ok for all
formats.
John
From: holvbphoto@cs.com (Vince)
Newsgroups: rec.photo.equipment.35mm
Date: 15 Oct 2002
Subject: Re: Radioactive SMC Takumar Lens
"Jeremy" jeremy@no-spam-thanks.com writes:
>I own 3 of these yellow lenses. I would like to know if anyone has any
>experience in safe storage. Even though their radioactive level is low, at
>least according to the information I've seen, I wonder if placing them in a
>film bag designed to block airport X-rays would be appropriate?
I have the 35mm f 1.9 Vinitar lens (Looks more like a short telephoto) which also will
give off a reading on a Geiger counter but so do Alpa and Beta rays which are
harmless, back during the 1964-65 World's Fair the hall of science had a thing
where they took your dime and expose it to Alpa and Beta rays and mounted it
for you. In closing I've never had a problem with this lens overexposing my
film I know the lens makers wouldn't sell such lenses.
Vince
http://www.holvbphoto.com
From: T.P. t.p@nomailthanks.com
Newsgroups: rec.photo.equipment.35mm
Subject: Re: Radioactive SMC Takumar Lens
Date: Tue, 15 Oct 2002
"Jeremy" jeremy@no-spam-thanks.com wrote:
>Finally, does anyone know if police or fire organizations typically have
>radiation detection equipment on hand? I would like to just have the
>radiation levels measured once, if only for my own peace of mind.
My goodness, you really are paranoid. Here in the UK, every city and
major town has a "Public Analyst" who will do such tests for a
commercial fee that's regulated by Government. Perhaps, even in the
USA, you might be able to access a similar service.
On the other hand, you should perhaps be more concerned about colour
casts in your photos. If you place these lenses in sunlight (even
protected by window glass) they will lose their yellow cast over
several weeks. My near mint 20mm Zeiss (Jena) Flektogon (M42 mount)
was very yellow when I bought it but is now as clear as it should be.
Beware, if it's also hot where you place the lens, the grease in the
helicoid can melt and find its way into places it shouldn't.
From: buc4evr@aol.comnospam (Buc4evr)
Newsgroups: rec.photo.equipment.35mm
Date: 15 Oct 2002
Subject: Re: Radioactive SMC Takumar Lens
jeremy@no-spam-thanks.com wrote:
>I just purchased an SMC Takumar 35mm f/2.0 lens, circa 1974, and found that
>it has the yellow cast on the optical glass that is characteristic of
>radioactive lenses.
>
>(If you do not know about radioactive lenses, check out this link:
>
>http://medfmt.8k.com/mf/radioactive.html)
>
>I own 3 of these yellow lenses. I would like to know if anyone has any
>experience in safe storage. Even though their radioactive level is low, at
>least according to the information I've seen, I wonder if placing them in a
>film bag designed to block airport X-rays would be appropriate?
>
>Also, can these lenses fog my film, if the lenses stay mounted on the camera
>bodies while awaiting completing the exposure of the roll of film? I
>sometimes have film in my camera for a couple of weeks, prior to taking out
>
>for photofinishing.
>Finally, does anyone know if police or fire organizations typically have
>radiation detection equipment on hand? I would like to just have the
>radiation levels measured once, if only for my own peace of mind.
>
>Thanks
These lens were made with Thorium to increase the index of refraction. This
is the yellow color you see in the "coating". Decay of the Thorium actually
results in higher levels of radioactivity as the lens ages due to production of
other radioactive daughters in the glass. One way to tell is to put the lens
face down on undeveloped photo paper for several days ( in complete darkness of
course). Then develop the paper. Dark spots will tell you there were gamma rays
emitted. A Thorium containing lens hanging from your neck will result in .7
mrems of exposure per year to you- compared to the background level of 300
mrems per year. So you can see the risk is pretty darn low.
Newsgroups: rec.photo.equipment.35mm
From: Patrick Draper newsgroups145@pdrap.org
Subject: Re: Radioactive SMC Takumar Lens
Date: 16 Oct 2002
Patrick Draper newsgroups145@pdrap.org wrote:
>Thorium decays to Lanthanium, which emits gamma rays. It's not a hoax, and
>there's several sources on the web where one can learn about the hazard.
I was incorrect on that. The main isotope of Thorium, Thorium-232 is quite
stable with a half-life of 14 billion years. But over time some of it
will decay into Radium-228 which has a half life of 5.75 years. A sample
of purified Thorium-232 will reach equilibrium in about 30 years, which means
that the radioactivity will grow to its maximum level in 30 years, and from
then on the radioactivity will remain constant.
The amount of radiation would depend on the amount of Thorium present. I'd
be concerned about particularly large pieces of glass like a heavy eyepiece
from a WWII tank sight or something like that. A small piece of glass
would have a lot less radiation because there's a lot less throrium to start
with. Those are probably relatively safe when compared to other radiation
sources like the normal background radiation level or a high altitude plane
ride.
I found this page: http://www.blackcatsystems.com/science/radiation.html
It has some information on detecting radioactivity for those who are
curious or concerned about their lenses.
--
Patrick Draper
Date: Mon, 28 Oct 2002
To: cameramakers@rosebud.opusis.com
From: "Joseph O'Neil" joneil@multiboard.com
Subject: Re: [Cameramakers] Aero-Ektar resolution
>Apparently the 178 f/2.5 isn't radioactive.
-snip-
Actually, yes, it is, or manyof them are. I own one. I set it
on a light table,a nd could not detect the "browning" that is often
referred to. But to be sure, I set the lens down on a sheet of tri-X 4x5
film, wrapped up light tight in a coupel of paper bags.
After about 30 hours, I processed the sheet film, and yes, sure
enough, you could see the "strikes". Not a lot, but definately
there. Kinda pretty actually.
of the 7 elements in the lens, apaprently the rear two or two near
the back are "hot". I checked it otu,a nd to make a long story short, as
long as you are not sitting ont he lens 8 hours a day, you should be fine
handling it. I probally got more radition the other day getting some
dental x-rays then I will from a few years use of this lens. But they are
"hot".
As for resolution, i have not had a chance to test mine out
yet. They are big.
joe
http://www.oneilphoto.on.ca
http://www.multiboard.com/~joneil
From: trapforcannedmeatproduct@hotmail.com (R. Charles Henry)
Newsgroups: rec.photo.equipment.misc
Subject: Re: AeroJet Delft old aircraft reconnisance lens info?
Date: 26 Nov 2002
Thanks for the information, guys :)
Some other bits of information that may or may not be relevant are
that the lens is slightly radioactive... which means it's probably
made from a glass containing a bit of Thorium? And I'm told it
may have been designed to be used with a field flattener near the
focal point.
Gee this was no cheap piece of kit!
From: hemi4268@aol.com (Hemi4268)
Newsgroups: rec.photo.equipment.misc
Date: 24 Nov 2002
Subject: Re: AeroJet Delft old aircraft reconnisance lens info?
Hi
It would be very unusal for a 12 inch f1.5 lens to be used for aerial recon. I
think it's a wide field star map lens. So the lens looks up to the heavens
rather then down on the earth.
An original cost for a lens like this would be in excess of $30,000 in mid 70's
money. It most likely has at least 8 elements in it to correct for color,
distoration and so on.
Larry
From nikon mailing list:
Date: Sun, 23 Feb 2003
From: "Patrik Maechler patrik.maechler@gmx.ch
Subject: Re: Radioactive lenses
--- In NikonMF@yahoogroups.com, Michael Briggs michaelbriggs@e... wrote:
> Does anyone in this group have one of these yellow lenses? Is the color
> yellow or brownish?
I have no Nikkor lenses with a yellowish cast, but my Vivitar Auto
35mm/f1.9 is yellowish and i measured radioactivity with a Geiger
counter some time ago. My Pentax M42 SMC Takumar 50mm/f1.4 has a
yellow cast too, but i am not sure if thorium is the reason. Both
lenses are good performeres, by the way.
A hint: I heard that this damages in the crystal structures of the
glass, causing this colour centers, can be 'repaired': When exposing
the lens to bright sunlight for some weeks, the yellowish colour
dissapeared. Maybe you have a nice bright spot behind a window in your
house so you can try it. Just be careful it's not getting warm so the
aperture blades may become oily.
Greetings from Zurich,
Patrik
From nikon mailing list:
Date: Sun, 23 Feb 2003
From: Michael Briggs michaelbriggs@earthlink.net
Subject: Re: Radioactive lenses
> Date: Sun, 23 Feb 2003
> From: "Mike \"vK\" Kovacs mike-kovacs@shaw.ca
> Subject: Re: Radioactive lenses
>
> I'd love to see that article! Interesting stuff.
>
> I'll add that I read the bit on lanthanide glasses somewhere on the
> web: I think in the medium format camera library list...but they
> could well be mistaken. Unfortunately their site has been offline
> for a few days due to some bandwidth issues.
That article is mostly a collection of news group and email list postings.
It contains good information, but also wrong information.
>
> What still seems strange to me is that there are low level lenses and
> some screaming hot lenses. You'd think you'd have to add a fair bit
> of thorium to affect the physical properties of the glass and might
> expect them all to get quite "hot". (like the Aero Ektars)
Where have you heard of lenses with low levels of radioactivity? The ones that
I have measured range from a few thousand counts per second to a few ten
thousand, using a 50 mm diameter Geiger counter. The range is understandable
from the size of the lenses and from whether the thorium glass is an outside
element, or located in the interior and therefore the exterior partially
absorbs the radiation. There were several types of thorium glass, with some
differences in the thorium content.
> Date: Sun, 23 Feb 2003
> From: "aekalman aek@netcom.com
> Subject: Re: Radioactive lenses
>
> Hi Michael.
>
> I happen to have two 35mm f/1.4 Nikkors, so here are the results of an
> informal test.
>
> Lens #1: S/N 3636xx (I wrote 3635xx in my last message, that was from
> memory). This is from the first series of this lens. Probably made in
> 1972. Factory-converted to AI. They don't make 'em like this any more!
>
> Lens #2: S/N 4393xx. This is an AI-S lens, production date unknown.
>
> Test #1: Visual. Holding each lens, aperture set to f/1.4, looking
> through the rear of the lens at some handwriting on a white paper
> sheet lit via incandescent (sp?) light, lens #1 is noticeably browner
> than lens #2. My wife also instantly saw the difference.
This is a strong clue that the lens has a thorium-containing element. Almost
always the thorium glass will be used for a positive-power elements, which will
be thicker in its center. Sometimes you can see that the lens is browner in
the center compared to the edges.
>
> Test #2: Coatings / reflections. Lens #1's reflections (when viewed
> from the front, I was looking at the reflections of the light source,
> three white globe lights) tend towards blueish-purple. Lens #2's
> reflections tend towards bluish-green. The difference in color is
> easily seen.
This tells us about the coatings that Nikon was using at the time the lens was
made.
--Michael
From nikon mailing list:
Date: Sun, 23 Feb 2003
From: Michael Briggs michaelbriggs@earthlink.net
Subject: Re: Radioactive lenses
> Date: Sun, 23 Feb 2003
> From: "Patrik Maechler patrik.maechler@gmx.ch
> Subject: Re: Radioactive lenses
>
> --- In NikonMF@yahoogroups.com, Michael Briggs michaelbriggs@e... wrote:
>
>> Does anyone in this group have one of these yellow lenses? Is the
> color
>> yellow or brownish?
>
> I have no Nikkor lenses with a yellowish cast, but my Vivitar Auto
> 35mm/f1.9 is yellowish and i measured radioactivity with a Geiger
> counter some time ago. My Pentax M42 SMC Takumar 50mm/f1.4 has a
> yellow cast too, but i am not sure if thorium is the reason. Both
> lenses are good performeres, by the way.
The screwmount Pentax SMC Takumar 50/1.4 may be the most common radioactive
lens. There are various models of this name, not all of which are radioactive.
I have measured the gamma-ray spectrum of one and confirmed that the radiation
is from thorium.
> A hint: I heard that this damages in the crystal structures of the
> glass, causing this colour centers, can be 'repaired': When exposing
> the lens to bright sunlight for some weeks, the yellowish colour
> dissapeared. Maybe you have a nice bright spot behind a window in your
> house so you can try it. Just be careful it's not getting warm so the
> aperture blades may become oily.
I have bleached out the color centers using several weeks exposure with a
fluorescent blacklight bulb. As I understand the process, UV photons will
allow electrons to overcome a potential barrier and eliminate the color centers
causing the brown color.
--Michael
Date: Thu, 10 Apr 2003
From: Michael Briggs MichaelBriggs@earthlink.net
To: cameramakers@rosebud.opusis.com
Subject: [Cameramakers] Re: Cameramakers digest
> From: "Kelvin" kelvinlee@pacific.net.sg
> Date: Wed, 9 Apr 2003
> Subject: [Cameramakers] Sun bleaching yellowed lenses
> Reply-To: cameramakers@rmp.opusis.com
>
>
> Hi guys,
>
> this may be of interest to some of you who have yellowed lenses ... for
> me,
> besides my super-takumars it is my nikkor 35/1.4 pre-AI. Apparantly you
> can
> wrap your lens in foil, front cap on, and face the rear element to the
> sun for
> a week and it reduces the yellowing (if not eliminate it).
A blacklight fluorescent bulb (BLB) also works, though perhaps taking longer.
I have treated two Aero-Ektars and a Nikkor-N 35mm f1.4 lens. It takes
several weeks this way, with the light on 24 hours a day. After a month, a 12
inch Aero Ektar still needs more time, probably because of the thick glass.
The fluorescent bulb might be easier for those in areas with infrequent
sunlight, or without a suitable window. Other fluorescent bulbs might work
better, e.g., the cheaper BL, but the BLBs are easy to find -- expensive at the
home supply chains, cheap at Walmart.
--Michael
From Camera fix mailing list:
Date: Wed, 9 Apr 2003
From: "Kelvin" kelvinlee@pacific.net.sg
Subject: Sun bleaching yellowed lenses
Hi guys,
this may be of interest to some of you who have yellowed lenses ... for me,
besides my super-takumars it is my nikkor 35/1.4 pre-AI. Apparantly you can
wrap your lens in foil, front cap on, and face the rear element to the sun for
a week and it reduces the yellowing (if not eliminate it).
I attach the post. This is an exciting development.
Gene: If you're on the list... maybe you can elaborate..?
Date: Tue, 08 Apr 2003
From: Gene Poon sheehans@ap.net
Subject: Sunlight vs. Yellow Peril: IT WORKS!
About the experiment to see if sunlight would bleach Yellow Peril, the
radiation-caused yellowing of internal elements afflicting the 7-element
50/1.4 Super Takumar, Super-Multi-Coated TAKUMAR and SMC TAKUMAR lenses
for the Pentax Spotmatic cameras:
IT WORKS!
It has only been since Thursday, April 3 that I put two 50/1.4 Takumars
on the windowsill. Since then, every day except Saturday has been at
least mostly sunny here in Northern California. Today I got a bit
impatient, and besides, I had to go into the box containing my Pentax
M42 stuff anyway, so I figured I may as well find out what was happening
and get out the rest of the 7-element 1.4 lenses to start on them, if
the sun bleaching was actually proceeding.
The experimental subjects were my very yellowest Super-Takumar and a
Super-Multi-Coated TAKUMAR which was moderately yellowed and had filter
ring damage and slightly stiff focusing. I figured I should experiment
with the two worst lenses, in case something bad happened. The UNCAPPED
lenses got completely wrapped in aluminum foil except for the rear
element, to reduce heat buildup in the sun, and also because doing so
would reflect light back through the lens, hopefully attacking the
yellowing from both sides.
This morning, after only five days, I unwrapped the lenses, and compared
the two experimental subjects with the rest of my 50/1.4 Takumars. THE
SUN BLEACHING WORKS! The two experimental lenses are now the least
yellow (the comparison is not even close) of all my 50/1.4 Takumars
except for the very early, 8-element Super Takumar that is not prone to
yellowing. Compared to that lens, and to the 55/1.8 and 55/2.0 lenses
which also are not prone to yellowing, there is still a slight tinge of
yellow, about the same as the pink tone from a weak skylight filter.
They are being rewrapped for another stay in the sun, and the rest of my
yellow Takumars are going to join the first two on the windowsill in a
few minutes.
Probably many Pentax M42 collectors and users will have Takumars on
their windowsills, very soon if not already!
-Gene Poon
From: "jriegle" jriegle@att.net
Newsgroups: sci.optics
Subject: Radiation discoloring of optical glass
Date: Thu, 10 Apr 2003
I am aware that optics manufacturers used some rare earth elements in their
lenses that are radioactive. A couple examples are some of the old 50mm f1.4
Super Takumar 35mm camera lens and the really old Kodak Aero Ektar lenses.
After years, these lenses have the optical elements that were radioactive
obtain a light yellow discoloration to them. One year ago, I purchased a
Super Takumar lens that had yellowed, bought it home and put it in front of
my Geiger counter. It sent the counter clicking wildly when placed very
close to the rear element.
I placed the lens in a sunny window sill and bleached the yellowing out in
about a month. The lens was then completely clear.
Physicists who work with nuclear radiation have found their laboratory
glassware to discolor after being irradiated. In some cases, it discolors in
minutes under strong doses. It appears to be gamma radiation causing the
discoloring. One source stated that his test tube turned yellow after 5
minutes of exposure from a strong gamma source (cobalt 60). It was found
that exposing the glass to light would 'bleach' away the discoloration.
I found one comment on the Internet by someone stating that the index of
refraction is changed slightly in the irradiated glass, causing it to be out
of spec. I haven't heard anyone complain that their Super Takumar was not
giving the excellent results that it had originally.
Can anyone (pardon the pun) shed some light on what is happening to the
glass to cause the discoloration? After light bleaching, is there remaining
damage, such as a change in index?
Thanks for your comments. John
From: Andrew Resnick andy.resnick@NOSPAM.grc.nasaDOTgov
Newsgroups: sci.optics
Subject: Re: Radiation discoloring of optical glass
Date: 10 Apr 2003
> Thanks for your comments. John
John,
There is quite a body of literature on the effects of ionizing radiation
on optical glass. Ionizing radiation (usually high speed electrons, but
also protons, nuclei, and high-energy photons) create what are called
'color centers' in glass. Briefly, the ionizing particle strips off
electrons from some of the atoms in the glass, creating a localized
defect. I am not familiar with the 'bleaching' that can occur upon
subsequent exposure to UV radiation. Radiation-induced changes to the
refractive index are of concern primarily to the deep-UV lithography
industry and the space industry, and a few papers I have that may be of
interest to you are:
Gusarov et. al., "Refractive-index changes caused by proton radiation in
silicate optical glasses", Applied Optics 41, 678 (2002)
Isbi et. al., "Enhanced photoinduced [chi]2 in gamma-ray-irradiated bulk
glass", Optics Letters 25, 902 (2000)
Al-Jumaily, "Effects of radiation on the optical properties of glass
materials", SPIE vol 1761, 26 (1992)
Griscom, D., "Nature of defects and defect generation in optical
glasses", SPIE vol 541, 38 (1985)
Williams, R. T., "Nature of defects and defect generation in optical
crystals", SPIE vol 541, 25 (1985)
This should get you started.
--
Andrew Resnick, Ph. D.
National Center for Microgravity Research
NASA Glenn Research Center
From camera fix mailing list:
Date: Fri, 23 May 2003
From: Gene Poon sheehans@ap.net
Subject: More Yellow Banished from Takumars
The following is from a Russian Camera discussion group, temporarily
off-topic to discuss curing the radiation-induced yellowing in 50/1.4
and 35/2.0 screw mount Takumars. Note the mention of the SMC PENTAX
50/1.4, an early K-mount lens with 52mm filter thread and the same
optics as the Super-Multi-Coated Takumar 50/1.4, confirming that those,
too, shall go yellow eventually.
"I am pleased to confirm that the Pentax lenses (Super MC Takumar
1.4/50, SMC Pentax 1.4/50 and Super Takumar 2/35 have all lost their
"tea" color after 4 weeks in front of the window. It takes a little
longer in Holland because sunny days are not very frequent. The Jupiter9
2/85 that I also put on the window sill is still as green as it always
was. At the beginning all 4 lenses were about equally dark, the 2/35
being the worst, but now the Pentax lenses are distinctly brighter than
the Jupiter, which served as a control."
From russian camera mailing list:
Date: Sat, 28 Feb 2004
From: "Roman J. Rohleder" rjrohleder@web.de
Subject: [Russiancamera] Es strahlt!
To: Russiancamera-user russiancamera-user@beststuff.com
David,
Franz, a friend of mine, received a FED5C just a few days ago. He bought it
to get a I61LD for his two Zorkiis, the seller was "uaphoto".
When he got the package from customs (he payd no fees), the box beared a tag
"Vom Zoll geoeffnet, Inhalt emittierte radioaktive Strahlung" - "opened by
customs, parcel contained a radioactive emitter!". :-)
From russian camera mailing list:
Date: Sat, 28 Feb 2004
From: David Nebenzahl nobody@nowhere.net
Subject: Re: [Russiancamera] Re: Obviously....
To: Russiancamera-user russiancamera-user@beststuff.com
Roberto wrote:
>
> Just for curiosity:
> http://home.att.net/~jriegle/radioactive.htm
Interesting link; thanks for that.
But this only proves a) that the Pentax Super-Multi-Coated Takumar 50mm f1.4
is indeed radioactive and b) that this particular specimen was yellowed.
Still doesn't prove that all radioactive lenses yellow.
Date: Tue, 25 May 2004
Subject: Re: [Contax] 35mm Distagon (distortion and stuff)
From: Bob Shell bob@bobshell.com
To: contax@photo.cis.to
Alexander wrote:
> a radioactive lens???
> I still have the 24 2.8 FD and the 35-105 macro FD. Any of those radio
> active?
>
This has been discussed many times on other forums. Some of the rare
earth salts used to dope batches of glass to get the desired dispersion
are radioactive. The famous Voigtl,nder Apo-Lanthar lenses used a
Lanthanum salt to achieve apochromatic correction. If you put one of
these lenses on top of a sheet of Polaroid film for a day and then
develop the film you can see the fog pattern produced by the radiation.
Pentax used radioactive salts in some Takumar lenses as well. No
lenses made today use radioactive salts because of concerns with the
health of the factory workers. Radioactive lenses are not dangerous in
normal use. If you want to have children you probably would not want
to sit with one in your lap for a couple of days, though.
Bob
From: "Norman Worth" nworth@earthlink.net
Newsgroups: rec.photo.equipment.35mm,rec.photo.equipment.large-format,rec.photo.equipment.medium-format
Subject: Re: Radioactive lenses - Oak Ridge Web site
Date: Fri, 21 May 2004
It's interesting that this does not mention the earlier lenses that
contained thorium. I understand that Th has been used in optics at least
since the 30s, and the AeroEktars (late 40s and early 50s) are famous for
it. External radiation is almost entirely from gamma rays emitted by the
daughter products of thorium decay. From the top of my head and looking at
the formulation given, it would seem that there is significant
self-absorption of gamma radiation in the lens itself. I wonder if that was
taken into account in calculating the dose rates. In any case, the
regulations have the force of law. I doubt if anyone has been harmed by
normal use of these products.
"Neil Gould" neil@myplaceofwork.com wrote ...
> Recently, Nicholas O. Lindan see@sig.com posted:
>
> > http://www.orau.org/ptp/collection/consumer%20products/cameralens.htm
> >
> Looks like a good addition for a variation of Olgierd's collection...
>
> Neil
From: "Nicholas O. Lindan" see@sig.com
Newsgroups: rec.photo.equipment.35mm,rec.photo.equipment.large-format,rec.photo.equipment.medium-format
Subject: Radioactive lenses - Oak Ridge Web site
Date: Wed, 19 May 2004
http://www.orau.org/ptp/collection/consumer%20products/cameralens.htm
--
Nicholas O. Lindan
Date: Tue, 21 Sep 1999
From: Richard Knoppow dickburk@ix.netcom.com
Subject: Re: [Rollei] Re: [Rollei] Off topic: Voigtlander
Lanthar
>> Its a Cooke triplet. The Apo-Lanthar is a Heliar.
>> The name may or may not refer to Lanthanum glass. I can't remember how long
>> Voigtlander has been using this name for a lens. Lanthanum is _not_
>> radioactive, I just checked a bunch of MSDS to confirm that.
>> Some radioactive materials have been used in glass formulas, notably
>> Thorium, which was used in a few WW-2 vintage aerial lenses because there
>> wasn't anything better at the time.
>> ----
>> Richard Knoppow
>> Los Angeles,Ca.
>> dickburk@ix.netcom.com
>
>I really hate to have to disagree with you, since I consider you one of
the
>most accurate posters here, but as I said we did not rely on published
info
>in determining "hot" lenses. Roger did film tests.
>
>I will ask him for more details and post here.
>
>Bob
Richard Knoppow
Los Angeles,Ca.
dickburk@ix.netcom.com
From: Bob Shell bob@bobshell.com
Subject: [Rollei] "Hot" lenses
> Radioactivity in the first generation of hot lenses c. 1941-1955 is a
> by-product of imperfect refinement of the monazite sands used to provide
> the rare earths. There are quite a few 'hot' rare-earth first-generation
> lenses, though it would take me a while to find the reference, and
> certainly, some of them were terrestrial: it has been suggested that the
> double shutter in the Voigtlaender Prominent was because the 50/1.5 Nokton
> -- the first new civilian rare-earth lens, as far as I know -- was 'hot'
> and could fog the film, though equally, this may simply have been extra
> insurance for light-trapping. Intriguingly, some Apo-Lanthars are 'hot' and
> others aren't, presumably reflecting different sources of lanthanum (or
> improved refining techniques from a single source). From recollection,
> these first-generation lenses were gamma-particle emitters, possibly with
> some beta (I'm not sure about the latter).
>
> Radioactivity in the second generation of lenses was down to the use of
> cerium to bleach iron salts in the glass; (colourless) ferrates are stable
> in glass solution. Once again, the purity of the cerium was questionable.
> These are alpha-particle emitters, which ain't normally a problem -- even a
> lens-cap stops the particles, as does a few cm of air -- but it's not a
> good idea to use the lens as a telescope eye-piece, as some did. These
> second-generation lenses stretched well into the 1960s; again from memory,
> at least one of the standard Takumars was 'hot'.
Newsgroups: rec.photo.equipment.35mm
Date: Fri, 28 Jul 2000
Subject: Re: Airport Xrays - Let's give it a rest
>Amen.
>
>I have tried in the past to provide info (based on very extensive research for
>an article in Shutterbug) but people prefer to hear the myths.
>
>The photo industry test results are on the PIMA web site http://www.pima.net
>(Note the difference between the systems used for CARRY-ON bags and for CHECKED
>baggage.)
Date: Sat, 23 Dec 2000
From: steven arterberry arterberry@mindspring.com
Subject: Re: [Rollei] OT: strange colour in a Jena Pancolar
From: "Guido Cova" guido.cova@tin.it
Sent: Wednesday, December 20, 2000
Subject: [Rollei] OT: strange colour in a Jena Pancolar
> > Some glass "stains" or turns brown. Good optical glass should not do
> this
> > unless subjected to intense radiation. A few lenses were made with radio
> > active glass during WW-2 and often the radio-active elements have browned
> > with age.
> Hi all.
> I have a Jena Pancolar 50/1.8 which is... yellow! I don't mean a light
> yellow fog, but really yellow lenses!
> It is absolutely fine for BW, but unusable with colour film.
> Does this yellow colour mean it has been made form radio-active glass?
> Should I be worried?
> Ciao
> Guido Cova
Date: Wed, 10 Jan 2001
From: Jem Kime jem.kime@cwcom.net
Subject: RE: [Leica] Radioactive lenses & the rabbit
From: goldman@math.umn.edu [SMTP:goldman@math.umn.edu]
Date: Thu, 04 Jan 2001
From: John Sonderegger medi8tor@pacbell.net
Reply to: medi8or@pacbell.net
To: rmonagha@mail.smu.edu
Subject: Re: Suggested addition to
http://www.smu.edu/~rmonagha/mf/ektar.html
>To Todd Gustaffson
>Director of Technology
>Eastman House.
>
>I have been searching for a long focal length lens to adapt to an overhead
>projector in order to increase the projector/screen distance substantially.
>Today acquired an old Kodak lens marked, Kodak Aero-Ektar F6.0 24in 610mm
>9x18 ER225 Made in U.S.A. By Eastman Kodak. I didn't notice it at the time
>of purchase but the rear element is slightly yellow/brown.
>
>When I arrived home I searched the internet for information on this lens.
>What I found was _very_ surprising. On
>http://www.smu.edu/~rmonagha/mf/ektar.html I found a message that
>indicates my lens is RADIOACTIVE! Is there a health risk associated with this
>lens?
>How radioactive is it? What sort of radiation does it produce? Does the 9x18
>marking mean it will cover a 9 inch by 18 inch film stock? Does that mean it will
>also cover an 18 inch by 18 inch area? Do you know what this lens was used for
>originally? Any information you can supply will be appreciated.
>John
Curator
Technology
From: Gary Reese pcacala@earthlink.net
To: rmonagha@post.cis.smu.edu
Subject: Message Board contribution
Las Vegas, NM
Date: Mon, 28 May 2001
From: Steven or Alison Bailey abbailey1@earthlink.net
To: rmonagha@post.cis.smu.edu
Subject: Re: Guido Cova - Pancolar 50/1.8 radiation
Date: Sat, 30 Jun 2001
From: Photoscientia photoscientia@photoscientia.co.uk
To: rmonagha@mail.smu.edu
Subject: Radioactive lenses
Date: Sat, 28 Jul 2001
From: Marc James Small msmall@roanoke.infi.net
Subject: Re: [Leica] Radioactive glass - follow up
>Marc - I do have an f2/50 collapsible #1278236, would this be early enough?
msmall@roanoke.infi.net
Date: Fri, 27 Jul 2001
From: "Hugh Thompson" painfree@istar.ca
Subject: [Leica] Radioactive glass in M lenses ?
Date: Fri, 27 Jul 2001
From: "Mxsmanic" mxsmanic@hotmail.com
Subject: Re: [Leica] Radioactive glass in M lenses ?
> Talking to a dealer this evening and he told me
> that glass in some 1950's M lenses is radioactive,
> and the lenses have added value because of their
> rarity.
Date: Fri, 27 Jul 2001
From: Marc James Small msmall@roanoke.infi.net
Subject: Re: [Leica] Radioactive glass in M lenses ?
>Leica and most other manufacturers of good lenses use special glasses to obtain
>the optical characteristics they require. At one time, Leica had its own glass
>lab, and at least one of the glasses it produced contained thorium oxide.
>Thorium is a mildly radioactive metal similar to uranium in its radioactivity.
>The use of thorium and lanthanum oxides made it possible to obtain very high
>indices of refraction with low dispersion, which is useful for correction of
>many aberrations.
msmall@roanoke.infi.net
Date: Sun, 29 Jul 2001
From: "Hugh Thompson" painfree@istar.ca
Subject: Re: [Leica] Radioactive glass - follow up
From: "Marc James Small" msmall@roanoke.infi.net
Sent: Saturday, July 28, 2001
Subject: Re: [Leica] Radioactive glass - follow up
>Marc - I do have an f2/50 collapsible #1278236, would this be early enough?
msmall@roanoke.infi.net
Date: Wed, 22 Aug 2001
To: rollei@mejac.palo-alto.ca.us
From: Matthew Phillips mlphilli@hsc.vcu.edu>
Subject: Re: [Rollei] Rollei Urban Legends
>This is great info. Let me ask about another Rollei Urban Myth... that
>somewhere in the T production run the Tessar was recalculated using higher
>index glasses which became more available and were more economical after the
>war...?
>
>
>Eric Goldstein
The Perleman Rollei Manual lists this change as the incorporation of a new
Lanthanum element.
Date: Sat, 01 Dec 2001
From: Michael Briggs MichaelBriggs@Earthlink.net>
To: rmonagha@mail.smu.edu
Subject: Aero-Ektars; your web page on Radioactive Lenses
Hello Robert,
I have enjoyed reading the information on your Medium Format webpages and
appreciate the work you have done.
As a several year long project, I have been researching the Kodak Aero-Ektars.
Much of the information on your page "Radioactive Glass in Lenses Are Your
Lenses Really "Hot"?!!" is correct, but some of the comments that you have
compiled contain incorrect statements. In my research I have tried to base
my conclusions on high-quality documents from the era in which the lenses were
made or from observations and measurements of the lenses. If you wish, you can
view my first effort at explaining my findings at
http://home.earthlink.net/~michaelbriggs/aeroektar/aeroektar.html. If you have
any questions, please ask. This will help me know what I am not explaining
clearly.
For your web page on radioactive lenses, you might want to include a disclaimer
that some of the compiled information is probably wrong. You are welcome to
link to my page, but I don't want the page copied to another site because I
plan to update it. Of course, my web page is only about Aero-Ektars while
yours is on the broader topic of all radioactive lenses.
--Michael
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Michael S. Briggs -- MichaelBriggs@EarthLink.net
Sent by XFMail running under Linux on 01-Dec-01 at 23:19:11
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
To: camera-fix@yahoogroups.com
From: flexaret@sprynet.com
Date: Sat, 22 Dec 2001 10:57:43 -0400
Subject: Re: [camera-fix] Yellow Lens. Hopeless?
Bob,
A real "Hot" lens is the Kodak Aero Ektar 178MM f2.5 aerial lens. This was
widely sold as surplus after WWII, when photo equipment was in short supply. They made focusing and other mounts for it and reflex housings for Leica-
It could fit 4x5 Speed Graphic, 35MM Exakta, Hassy 1000F etc. These lenses
might have "Thorium" in them.
I have two - one in the Exakta focusing mount and one I adapted for Bronica
S2A.
When I got a geiger counter and checked these lenses and the thing was
really clicking I have put them in insolation here at home.
Contacting Kodak, they tried to minimize it, but I countered with there was
no warning to the public when these military lenses were sold to the public. Kodak safety department sent me some gobbledegook letter to explain it.
HOWEVER - Kodak's own George Eastman House camera museum had a box
containing some of these lenses and when they found out about the radioactivity - they dumped them and fast.
Maybe Kodak is afraid of a massive class action suit on this subject as the
lenses should have beeen labeled as such.
However, they were designed for the miltary in WWII for night aerial
photography, when we were only concerned about winning a war. The thought that military cameramen might get a little radiation - we all know there is risk in the military. I don't think anybody ever conceived at the time of massive
amounts of these lenses sold to the public, and it would be hard to prove that anybody was ever hurt by one unless it fell off a high shelf onto his head.
Re- Carl Zeiss Jena 50MM f2 Pancolar - in 42MM mount-
The only lens I once had which was so yellow it looked like it had a yellow
filter.
Don't know about radiation - but if one likes such a lens - there must be
some light blue or other filter which might normalize it.
- Sam Sherman
----------
From: Bob Shell bob@bobshell.com>
To: camera-fix@yahoogroups.com>
Subject: Re: [camera-fix] Yellow Lens. Hopeless?
Date: Sat, Dec 22, 2001,
> From: kelvin kelvinlee@pacific.net.sg>
> Date: Sat, 22 Dec 2001
> To: camera-fix@yahoogroups.com
> Subject: Re: [camera-fix] Yellow Lens. Hopeless?
>
> a listmember on the spotmatic group who is an expert in
> this says there is nothing to worry about. The
> radioactive decay consists of hardless electrons being
> released. Less than environmental radiation one gets
> walking outside on a bright day.
Well not everyone knows what they are talking about! g>
You can put one of these lenses on a single sheet pack of
4 X 5 Polaroid film for a few days and then process the sheet
and you will see fogging. Harmless electrons?? Hardly.
In normal situations these hot lenses are not dangerous,
but you wouldn't want to sleep with one under your pillow!
The reason the optical companies stopped using hot glass was
due to the danger to workers in the manufacturing process,
not danger to the end users.
Bob
To: camera-fix@yahoogroups.com
From: rolohar@aol.com
Date: Sat, 22 Dec 2001
Subject: Re: [camera-fix] Yellow Lens. Hopeless?
bob@bobshell.com writes:
> I can't speak for Roger, but I still have my "hot" Apo-Lanthar.
>
> Bob
>
I was just sitting here and looking at several cameras on the shelf that have
cloth focal plane shutters. I wonder what would happen to my film
if I mounted one of those "hot" lenses on a camera with a cloth shutter?
Would I ruin the film? Or perhaps degrade the shutter material over years of
being in close promimity to the "hot glass"
Also, my wife tells me(eavesdropping on my email) that certain earthenware
crockpots and baking dishes have been known not only to contain lead, but to
be radioactively contaminated.
Anyone ever heard of this? (I'm smart enough not to tell my wife that she is
wrong).
Roland F. Harriston
To: camera-fix@yahoogroups.com
From: Robert Monaghan rmonagha@post.smu.edu>
Date: Sun, 23 Dec 2001
Subject: [camera-fix] will feds confiscate "hot" lenses? re: radioactive lenses
besides the fact that many of us have these "hot" lenses (some who
don't know it), this may also become an issue shortly if you try to mail
one of these puppies off to be repaired in the USA, or sell one on ebay
The reason is the high levels of beta/gamma radiation would likely trigger
nuclear anti-terrorism detectors which one can presume are being installed
at various points in the US mail system to detect radiation from
potential terrorist "dirty" radioactive bombs and plutonium contaminated
letters and devices sent thru the mails and packages system etc.
Will the feds take the easy route of just confiscating these hot optics as
unlicensed radiation sources? Or do you think they will just let us mail
these radioactive lenses around and trigger costly nuclear alerts in post
offices all over the place? Duh? Wanna bet your Leica summicron on that? ;-)
from michael's interesting page on aero-ektars at
http://home.earthlink.net/~michaelbriggs/aeroektar/aeroektar.html
quote:Because our laboratory was recently moved, my calculations have not
been tested by measurements of the intensity. I do NOT guarantee the
correctness of these calculations. endquote
The reported MEASURED radiation levels I have seen on aero-ektars are 1
millirem/hr and 1.5 millirems/hr. For a particular aero ektar sample lens,
the British Journal of Photography, March 20 and October 29, 1987 has some
articles reporting 850 counts/sec of beta/gamma, and 320 c/s of gamma
alone. Similarly, Leica summicron measurements of intensity for 6 lenses
averaged 1.5 millirems/hr as well for early serial number "hot" optics.
The USA lifetime exposure limit for a radiation industry worker (nuclear
power plant etc) is 5,000 millirems - meaning rather less than one
millirem per day on average (25 years x 200 workdays/yr). These lenses are
putting out 1 to 1.5 millirems per HOUR, with much of that being penetrating
gamma rays in the cited sample. Starting to see a problem here?
The reported gamma ray level of 320 counts/sec from an aero-ektar is WAAAY
above typical background radiation levels (like over 100 times normal
background levels). These are much hotter than the licensed gamma
standards we have to store in lead "pigs" in our campus science labs etc.
Since the size differences here are huge, I would question the assumption
that the radioactivity is solely related to the amount of thorium used,
given the big 4" aero ektar lens elements are much larger than those in
the Leica, while the Leica lenses are often of higher radioactivity. Yes?
So the problem isn't the radiation from thorium or lanthanum itself,
but rather the varying levels of contamination by other more highly
radioactive isotopes due to insufficient purification years ago. Better
purification methods in more recent batches of thoriated glasses have
removed these chemically similar radioactive contaminants, so current
lenses are much less radioactive (due mainly to the thorium content now).
So the C.F.R. exemption Michael cites for recent thoriated glasses would
not necessarily apply to other radioactive contaminants present in the
older glasses making them much more radioactive than might be predicted by
calculations based on thorium alone. Instead, these more radioactive "hot"
older glasses would presumably have to be treated as unlicensed sources
and low level nuclear waste since their gamma and beta levels exceed
US/European standards in these cited examples.
But note that measurements on a few lenses would not guarantee that other
batches were not more or less contaminated, possibly by a large factor.
Even lenses within a batch could vary greatly too. So each lens would
have to be individually tested for its actual radioactivity levels.
Understand that I am very much in favor of anti-nuclear terrorism efforts
and support such efforts wholeheartedly. But I would expect to learn that
many of our "hot" radioactive lenses now exceed safety standards and are
subject to confiscation when detected in the mails and burial as low level
radioactive waste.
The "good" news is that there is probably a great class action law suit
here, given the degree to which various photo industry major players have
actively denied they made radioactive lenses for years, and/or downplayed
the safety hazards, thereby hiding what they knew to be a product defect.
So this may become an even more "hot" topic in the industry ;-) grins bobm
To: camera-fix@yahoogroups.com
From: Michael Briggs michaelbriggs@earthlink.net>
Date: Sat, 22 Dec 2001
Subject: RE: [camera-fix] Yellow Lens. Hopeless?
On 22-Dec-01 camera-fix@yahoogroups.com wrote:
> Date: Fri, 21 Dec 2001
> From: "Dude6473527" rhettanderson@yahoo.com>
> Subject: Yellow Lens. Hopeless?
>
> I stumbled upon a nice Zeiss Jena Pancolar 50mm f/1.8. It has these
> problems:
> 2) The lens is very yellow when mounted on a camera (no, it's not the
> camera--it's yellow on 3 different m42 cameras).
>
> First of all, is it hopeless? I suppose it could be used for B&W;
> photography, but that seems a shame. Is there anything which can be
> done to get rid of the yellow?
>
> Second, what did a previous owner do wrong to cause this? I've
> handled hundreds of used lens, and never seen a color cast like this.
>
Is the lens a chromatically pure yellow, or more of a yellow/brown color?
I have been researching the Kodak Aero-Ektars--I describe their color as
similar to tea. A draft description of my findings on the Aero-Ektars is
available at http://home.earthlink.net/~michaelbriggs/aeroektar/aeroektar.html.
The Aero-Ektars are radioactive because of intentional inclusion of Thorium in
some of the glass; I think it extremely likely that the brown color of the
Aero-Ektars is self-induced radiation damage.
IF your Pancolor lens is yellow because of radiation damage, it is very likely
to be from Thorium glass. You can test for radioactivity by using a
Geiger-counter (which you probably don't have) or by making a one week or
longer exposure on film. You can use regular film or Polaroid sheets. I use
ASA 400 film in a 4x5 sheet film holder.
As a guess, the Aero-Ektars are probably the most radioactive lenses because of
their large size. Their radioactivity is of a level that should be treated
with respect. My advice is to keep the lenses far away from people when not in
use. One indication that thorium containing lenses are reasonably safe is
that their possession is legal in the USA--see the web address given above.
Much of the information on the internet about radioactive lenses is either
misleading or incorrect. I suggest asking yourself what the evidence is for
any statement that you read.
--Michael
P.S. I would be interested in receiving via email to
MichaelBriggs@earthlink.net (this would bore others on the list) the data
inscribed on any Aero-Ektars that anyone has: focal length, format, serial
number, etc. I am trying to determine how many types were made and in
approximately what numbers.
From russian camera mailing list:
Date: Mon, 12 Nov 2001
From: Bob Shell bob@bobshell.com
Subject: Re: Color correction for older Jupiters?
The easiest way is to put the lens down on a 4 X 5 sheet of Polaroid 3000
film for a couple of days, then put the sheet in a holder and process it.
Bob
> From: Blanka007@aol.com
> Date: Mon, 12 Nov 2001
> To: russiancamera@yahoogroups.com
> Subject: Re: [russiancamera] Color correction for older Jupiters?
>
> There was a technique described somewhere how to check lenses for
> radioactivity. It had something to do with placing a lens in question on a
> sheet of photo paper (in a usual black case) for several days. A hot lens
> would fog the paper in a certaing pattern.
> But the test I've heard about was done with a Geiger counter.
From Minolta Mailing List:
Date: Mon, 15 Oct 2001
From: "Franka T. Lieu" Franka_L@Pacific.net.hk>
Subject: Re. really hot (radioactive) lenses
The only known lens that are really HOT is the original UK version of
the War Time production Kodak " Aero Ektar" for the War Department.
I've seen sample of them when I attain my safety course on such
matter. They come in a sturby wooden box lined with lead. I was told
by the instructor also that these are some of the earliest industrial
use of radioactive material other than the nominal medical use. These
lens are all known to be very unstable and fortunately most are
disposed of ( properly ).
From Minolta Mailing List:
Date: Mon, 15 Oct 2001
From: lmhample@mindspring.com
Subject: Radioactive Minolta Lenses
So does anyone know which Minolta lenses are radioactive? It sounds
as if the oldest 58/1.2's are, but not the newer ones. What about the
58/1.4's and 35/1.8's? Is there anything resembling a comprehensive
list? Is it safe to say that if the lens has yellowed, then it is
radioactive? (What compensating filter would be appropriate?
Presumably, the filter would also shield alpha and beta particles
from the front.) I read Robert M's web page on radioactive lenses,
but I didn't come away understanding just how hazardous these lenses
are to use? Should I keep them away from my kids, should I get rid of
them or should I not worry about it? Also, I didn't understand if all
lenses containing lanthanum are radioactive or would newer ones be
'cool'. I ask because I use Vixen Lanthanum eyepieces with my
telescope. Thanks for any info.
From Minolta Mailing List:
Date: Mon, 15 Oct 2001
From: plumaman@aol.com
Subject: Re: Radioactive Minolta Lenses
If you go to http://www.energy.gov, they should be able to answer you
questions or lead you in the right direction.
I have never heard of anything becoming more radioactive with age so
I would take the letter you were refurred to with a grain of salt.
Chuck
From camera fix mailing list:
Date: Wed, 18 Sep 2002
From: "Mark Stuart" madfamily at bigpond.com
Subject: Yellowed Takumar 50mm f1.4 cure
Hi guys,
I've just visited our local old camera guru repairer who is also a
Pentax buff (has SP through to MZ-S) and was discussing the 50mm
yellow curse. He said with some authority that the problem is not the
element itself that yellows, but the Canada balsam in between element
1 and 2 (I think) from the mount end. The radioactivity causes the
problem via its proximity to the balsam, but it's not the glass that
yellows.
He has actually fixed this on a couple of lenses, but unfortunately
it's well outside of economic reality (AU$140). He admitted this, and
said that the owners of the two he's done insisted. Colour rendition
etc. was as per new.
Can any of you pros confirm this? How hard is this to do yourself?
Thanks
Mark