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From: Linda A Whatley linda_aw@ix.netcom.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re:Cementing Lenses
Date: Thu, 02 Apr 1998
Edmund Scientific supplies "Balsam Mounting Fluid, for
microscope slide preparation, in lots of three 1-oz. bottles.
It cements lenses just fine. I'll send you one of the ounces
I have here, if you wish; I doubt if I'll be running short
any time soon ;-)
- Larry Whatley
From: "skgrimes" skgrimes@ma.ultranet.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Lens Cementing Adhesive Source
Date: Tue, 7 Apr 1998
Summers Optical company also sells lens cement and takes small orders with
credit cards. There is a link to their site in my page of links. Also, I
found an old article from Popular Science (1944) which I have repuplished on
my site for the general entertainment. The techniques can be used with the
modern cement as well. SKG
---- S.K. Grimes -- Feinmechanik ----
From: superwide@jccomp.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Lens Cementing Adhesive Source
Date: Tue, 07 Apr 1998
There are a number of adhesives made for lens cementing. All of these are available from the Edmund Scientific Company. They have a web site. The main problem with using these adhesives are that they must be cured with UV light. A UV light source having sufficient power to completely cure a lens in a reasonable amount of time is relatively expensive. They are also in the Edmund catalog. The sun can be used easily. Another option is to search for a old incandescent type sun lamp. I have seen these in second hand stores selling for about $9.00. I recently re-cemented a Zeiss rangefinder prism using the UV adhesive and a sun lamp from a second hand store. It worked very well and took about an hour to completely cure the adhesive. The Edmund catalog also contains an epoxy type two part lens cement. This is recommended by them to be used only for light duty work. The UV curing cement cures with great strength. I hope this helps.
Date: Fri, 03 Apr 1998
From: Richard Knoppow dickburk@ix.netcom.com
Subject: RE: [Rollei] Voigtlander Heliar
At 11:36 PM 4/2/98 -0700, you wrote: >Gentlemen, > >I have had two Bessa II cameras, one with a Colour Skopar and the other >with a Colour Heliar. I had always wondered what the differences in the >lenses might be as the Heliar has a reputation as a stellar >performer...although the Skopar was reported to be no slouch either. > >Filling both cameras with Fuji RDP (transparency film) I took them into the >studio and shot a table top setup with electronic flash (Speedotron >2400WS). The only thing in the whole setup that changed was the cameras. >And this I tried to keep as similar as possible. (I checked focus with a >ground glass on the film plane of both cameras before loading film so as >not to trust the rangefinders). > >When I got the two developed rolls back one was quite warm, as if I had >used a strong warming filter on it. Whites were yellow casted. The other >film was neutral. The warm casted film also was not as sharp as the neutral >one, almost as if a slight soft focus filter had been applied..no halos >though..just a bit soft over the whole depth of field that should have been >sharp. I definitely had the whole "sharp" depth of field in the frame on >both rolls. > >The neutral, sharp film came from the Colour Skopar equipped Bessa II. The >warm, slightly soft film came from the Colour Heliar. I checked the lenses >for any defects and found none, paying close attention to the Heliar. > >It is possible that the Heliar lens was defective, but I doubt it. The >camera was in near mint shape, which doesn't prove a lot...but does say >that it was probably not abused in its life time. Perhaps the Heliar was >not a great lens for colour work, not being able to bring all colours of >light to focus on the same plane, but was great at B/W work, hence the Apo >Lanthar? I did not shoot any B/W film. Needless to say I sold the Heliar >Bessa II. > >I have no great knowledge of Voigtlander cameras and lenses...just this >test I did. > > >Todd > > > It would be interesting to hear from others who have had experience with the Heliar. It should be at least equal to the Skopar. A strong difference in color rendition would make me suspect that the cement layers were starting to yellow, which can happen with Canada Balsam. Usually glass absorption or differences in coatings will make a rather subtle difference in color rendition. The slightly soft appearance of the Heliar photos also makes me suspicious that something was out of whack with it. The Apo Lanthar may be a better lens but the Heliar is well achromatised and has a reputation for being extra sharp. It may also have had some accumulated haze in it. Older lenses tend to get a hazy coating on the inner surfaces. Probably stuff evaporated from the anti reflection paint inside the cells. This can decrease the contrast of a lens to a surprizing extent. Almost all lenses more than perhaps forty years old I've encountered have this haze to some extent. Its easy to clean off once you get the cells open. Plain old Kodak lens cleaner does it. Shinning a flashlight through the lens will show it up right away. I suspect this haze is often the real culprit when old, uncoated, lenses are found to have low contrast. The haze could also give the light a color cast. ---- Richard Knoppow Los Angeles,Ca. dickburk@ix.netcom.com
From: "skgrimes" skgrimes@ma.ultranet.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Cementing Lenses
Date: Sat, 4 Apr 1998
Richard's comments are accurate. The distinction between original centering
then grinding of the lenses during manufacture and the easier task of
replicating this in repair should be noted. For same size lenses of good
manufacture the use of V-blocks will suffice. Place the lens concave side
down on a flat plate and arrange like this:
Different size lenses can be centered by using a projecting collimater
arranged vertically under a hollow turning spindle. The first lens is set
into the turning chuck or fixture and a video microscope (or simple video
camera with closeup attachment) is focused on the image. (You test and
prove the setup by placing a known, good quality lens in the chuck and turn
the spindle by hand. The image on the video screen should remain in the
same place and have no runout or eccentric movement. The element to be
cemented is placed, with its mate in the chuck and moved around so that the
video image has no runout. Turn on the UV lite and cure the cement.
I have observed this method in use at several optical shops.
SKG
From: "skgrimes" skgrimes@ma.ultranet.com
I'll be adding some comments to this essentially useful article including
some pics of techniques I use. Not everyone can afford or even find at any
cost a genuine Zeiss Optical Pocket Knife although Chinese Optical Frying
pans have become more common in recent times.
Seriously, this is where an amateur has the advantage: I avoid doing any
lens with a "rolled in" or "burnished" mount (unless its my own property) as
the risk of damaging the glass is a throbbing reality. But the
do-it-yourself enthusiast has little to lose and might get lucky. And if
the glass breaks he can spend the rest of the day in the park! SKG
[Ed. note: for information purposes only, no guarantees, caveat
emptor...]
Date: Sun, 26 Apr 1998
The coating on the 2.8 Planar seems to be very soft and perhaps with age
and due to oxidation, gotten even softer. But remember that it is only one
element in your lens that has lost a bit of its coating. All other elements
are coated and probably still have their coating as they are not subject to
the same wear that the front element is exposed to. The purpose of coating
is to increase the amount of light transmitted through a lens (resulting in
higher contrast images) as well as to correct for colour casts if needed.
If the front element were to lose all of its coating, I'm sure that there
wouldn't be a huge difference in the resulting film, in fact one may have
to look very hard to see any difference at allas there are still many
surfaces in a Planar that are coated.
I suspect that Chris, who mentioned that his lens was "cleaned", actually
has had the coating removed from the front of his lens and that the results
that he gets is not different than before he had his lens "cleaned".
Another problem with the 2.8 Planar is lens seperation of the front two
cemented elements, the 2.8 Planar seems to be predisposed to this condition
that some seem to think is coating damage. Lens separation in th 2.8 Planar
is characterised by "darkish" looking shapes if held to the light in the
right way. These darkish shapes are not sharp looking, but are continuous
and curiform and are found towards the outer edges of the lens. Ocasionally
the separation, when held to the light in a particular manner will show a
slightly reflective/refractive nature.
To correct lens separation in a Rollei TLR Planar is not that difficult,
but requires a batch of chemicals. The cement used to originally hold the
two elements together is not Canadian Balsam, but I think is a synthetic
optic glue. I take the front cell out of the Rollie by using a rubber disk.
Then dismantle the front cell...pretty easy to do , but there is a tiny and
I mean tiny set screw that holds the whole front cell assembly together.
After removing this screw, the capping plate that holds the whole thing
together simply screws off and the elements are free to be removed. The
font cemented doublet I drop into methylene chloride, which is the active
ingredient in paint stripper. I have also used paint stripper. Both work
and both do ABSOLUTELY NO harm to the coating and glass. Beware thought
that paint stripper is caustic and can etch some types of glass. Oh, and
make sure that you put the methylene chloride in a glass container with a
metal lid (canning jars are great) so that you can watch the progress of
the separation without having to remove the lid, as methylene chloride is
very nasty stuff and you want to have as little exposure to it as possible.
The doublet takes about a week to a month to come unstuck using just
chemicals. If it were canadian balsam it would come apart in a matter of
hours to a day. It can be hastened after a week by removing from the
chemicals and placing on a very low heat. I put mine on my metal desk lamp
which has a 60 watt bulb in it. Heating can cause the elements to crack if
they are still stuck together or the heat is too high as they expand at
different rates. I prefer being patient with the methylene chloride. The
elements should sort of slide apart with some resistace as it is an airless
bond. The lens surfaces sould simply wipe clean and if not, put them back
in the methylene chloride to soak until they come clean. Should only take
an hour or do. To put them back together you need UV optic glue, which
cures on exposure to UV light, so a few hours in sunlight will do the
trick. You can get the glue at Fargo Enterprises who advertise in
ShutterBug. Slide the two elements with glue together to avoid getting air
bubbles...it may take a few tries....then bake in the sun for a few hours.
Remember to paint the edges of the lenses black before putting the whole
thing back together.
When I did my first Planar, I was surprised at the curvature of the glued
faces. It seems MUCH greater than in the drawings that I've seen as well as
the thinness of the front element. I suppose this coupled with the fact
that the two pieces of glass are very diferent densities results in the
Planar being prone to separating.
I think that you will be surprised at how easy this is. Try on a junk lens
that you know has cemented pairs before trying the Planar
todd
Date: Sun, 19 Apr 1998
The viewing lenses on Rolleicords have set screws in the side of the
barrel. You must really remove the front of the focussing panel to get at
the lens.
Be _very_ carful to note the orientation o the center element and
spacers. The center element is very nearly bi-convex but not quite so the
lens will not work right if its reversed when re-installed.
I've found viewing lenses on a couple of rolleicords which had what
appeared to be oil on the inside surfaces. I don't know what the substance
was but it came off with lens cleaner.
----
Date: Mon, 06 Apr 1998
Date: Mon, 27 Apr 1998
I have heard that acetone does the job. I have also heard that if you use
Canada balsam to recement them, it may take centuries to dry... Does
anyone know if this operation can be done in an optical shop (once the
pieces are separate)?
Dante Stella
Date: Mon, 27 Apr 1998
John,
Yes. If Canada Balsam is the cement of choice, then Methyl Hydrate can be
used to unglue the elements. A step up from that would be Acetone, then the
methylene chloride. Methyl ethyl acetone will also work, but I think that
it is going to be placed on the hazardous chemical list.
Date: Mon, 27 Apr 1998
Date: Tue, 28 Apr 1998
Yes, you can subsititue cements. The thickness should be minimal but I
don't have any numbers on it. A thinner layer will bond better. The index
of refraction for most cements is similar to glass and the layer is so thin
it has no practical effect.
Can't answer the last. I have noticed some differences in very old
lenses by manufacturer but that may be only the lenses I've encountered. I
see very few pre-WW2 Zeiss Jena lenses with separation but it seems
frequent with some other brands. Possibly a difference in the grade of
Balsam or technique. It would be interesting to hear from others to see if
this is just an illusion.
The only books I've ever seen with any details of how lenses are made
were published in England in the mid-thirties and late forties by a
manufacturer of optical shop equipment. The title is "Optical Shop
Practice" but I can't remember the name of the company at the moment. They
are very rare, the L.A. public library has copies of two editions. These
go into cementing practices and talk about various grades and hardnesses of
Balsam. Probably most of the techniques described in these books have
changed now.
Summers Optical has some hints on cementing lenses on their web site:
http://www.emsdiasum.com/Summers/optical/cements/msds/default.html
----
Date: Tue, 28 Apr 1998
John,
Regarding the last question. I think (emphasis on think) that old lenses
are not as subject to separation as newer ones due to the less radical
differences in density of glass that are cemented together. Some modern
lenses (50s to present), I think, have more radical designs, greater
curvatures of surface, greater differences in densities of glass cemented
together, than the older lenses. All these factors can lead to a greater
propensity for a doublet to separate. Also the tightness of the lens mount
can have an effect, as a sharp temperature drop or rise could cause the
mount to tighten about the doublet. Repeated experiences could cause a
suseptible lens to start separating.
Regarding Richards heating method of lens separation: This is a viable
method, and I think the more traditional method, but in my experience is
riskier than just dropping the doublet into some chemicals and waiting
longer. I have cracked two lenses by heating before I tried chemicals (the
density difference thing I think). I would rather not use heat if
possible. As mentioned, though, I will resort to it once the lens appears
to be unsticking and has been in the drink for a while, and then it is a
very minor, almost warming heat. This is for the synthetic glue.
todd
Date: Tue, 28 Apr 1998
It may be because the cameras best cosmetically preserved spent a lot of
their life in attics, where the ambient temperature often fluctuates by 50
degrees at a time. User cameras ("junkers") often travel with people who
know enough to move away from the heat or cold (or at lease use A/C). Even
if they bang up the bodies, professionals know enough to take care of the
lenses. It's the tyro with the heavy hand who ruins the coatings...
Mr. Heinz Grasshoff, who was a Rollei tech and now a repair guru, once
told me that you have a 25% chance of finding separation in Rolleis made
before 1960. He said when he was at the plant in Braunschweig (I think),
they could not get decent lens cement (postwar this is no surprise). This
may explain why you rarely see separation in Tessars pre-WWII. I don't
know if this goes for the Schneiders as well, or where Rollei was
assembling the lenses.
With all the technology available to them, it is surprising that modern
eyeglass shops could not be used to cement these elements (if anyone has
the lab capability, it would be they). In fact, it would seem that they
would be able to re-coat as well. The anti-reflection coatings on
eyeglasses could not be that different from that on camera lenses (take a
hard look at the coatings on Seiko lenses. they have better antireflection
than most camera lenses).
Date: Wed, 29 Apr 1998
Hello,
I wouldn't advise you to "learn" lens repair by practicing on Zeiss lenses,
and if you don't have some good span wrenches, you shouldn't be messing
with any lenses. BTW...the easy part is taking the lens apart....the hard
part is getting them back together with less dust and marks than you
started with.
With that said... generally, after you remove the front filter ring (on the
50/1.8 by unscrewing it), the front lens group can be removed with a span
wrench. The rear group is more difficult...you can remove the outer most
element, but to remove the inner rear element(s) you'll need to disassemble
to focus helix. If you've never done this, I would strongly suggest you
don't start with a Zeiss lens. Pick up a damaged 50/1.8 and
practice...I've gotten two 50/1.8 Planars on eBay...one with some fungus
for $25, and another with missing rubber for $35. Both were fixable
including the fungus.
Finally, the 50/1.4 and the 85/f.2.8 are valuable lenses that are
definitely worth spending $50 each to have them professionally cleaned. If
you insist on trying...start with the 50mm f/1.8. If you trash it, your
only out $60 or so.
good luck,
Date: Wed, 29 Apr 1998
Most prewar Zeiss lenses mounted in shutters (and maybe some postwar--I'll
have to take a look) had the last several digits of the serial number from
the front ring stamped on the rear lens cell, so you can avoid mixing them
up. If Rollei did this with a batch of 2.8As, the lenses must not have
been mounted into numbered metal holders.
Date: Tue, 28 Apr 1998
The easiest way to separate lenses cemented with Canada Balsam is to heat
them.
They can be heated on an electric frying pan set for low heat or even by
putting them in hot (but not boiling) water. Heated this way they will
come apart in a few seconds.
Lenses cemented with synthetic cements may be much harder to get apart.
Sometimes they must be shocked apart by dipping them in hot oil but that
takes the risk of shattering the lenses.
I have found some lenses cemented with early thermo-setting cement which
had started to separate come apart completely with the same hot water
treatment that works for balsam.
You can find an asssortment of optical cements and solvents at:
http://www.emsdiasum.com/Summers/optical/cements/msds/default.html
Re-cementing lenses is not too difficult, especially if only two elements
are to be cemented.
Canada Balsam is still available, usually in liquid form, from seveal
suppliers. I got some here in LA from Tri-S Sciences, who specialize in
selling small amounts of chemicals.
The liquid balsam must be allowed to dry out and then heated to get to
flow or the lenses will take forever to cure. Synthetic cement is better
but Canada Balsam is still useful since it is so easy to get apart again if
you goof.
----
From: cg@evrl.xs4all.nl (Cees de Groot)
nwester nwester@olympus.net said:
You can give heavy molybdene grease from a car parts shop a try, it
should be heavy enough for this. As mentioned, Curt Fargo has a load
of specialized greases in case this doesn't work out. Never used them,
I try to cope with just molybdene grease, lithium grease, and shutter oil.
--
From: "skgrimes" skgrimes@ma.ultranet.com
In the case of lubricating the focus mount the right technique is more
important than the right stuff. Your trick of softening up the old grease
with lighter fluid may be good enough and help keep you out of worse
trouble. You have to trade off your unknown ability to disassemble, clean,
asses the nature of the lubricant needed and re-assemble the mount against
the advantage of leaving well enough alone. Multiple start threads as used
in focus mounts can be a challenge to re-assemble and you risk damage from
inexperience.
A little lighter fluid or solvent avoids these problems.
Which lubricant to use has more to do with the design and manufacture of the
mount than the lubricant. Some mounts are made with very fine, close
fitting threads which require a light lubricant others are made with
coarser looser fitting threads which require a thicker grease.
There is no one "right" lubricant for focus mounts. And experience is the
best guide to which to use in any specific case, so that the right touch
is acheived in the finished assembly.
There is also a complicating factor, especially important in auto iris
lenses (such as 35mm cameras) to avoid lubricants which can "gas out" ;
This results in the common problem of oily condensate on the iris blades
which interferes with their operation. SKG
---- S.K. Grimes -- Feinmechanik ----
rec.photo.equipment.large-format nwester wrote:
P>
rec.photo.equipment.large-format
nwester wrote:
I have used valve oil as found in musical insturment stores and used on
trumpets and other valve type insturments.
From: dickburk@ix.netcom.com (Richard Knoppow)
Old lenses were cemented with Canada Balsam. They can be gotten
apart with gentle heating. Heat on an electric frying pan set to a
low temperature or in heated (not boiling) water.
Later lenses were cemented with thermo-setting synthetic adhesives.
Currently, UV curing cements are used. Edmond Scientific and Fargo
Enterprise both cary the UV cement. Its not too expensive but the
cheapest UV curing light is about $500 US. I have not tried this
stuff with simple UV sources so don't know of they will work.
Suposedly Mercury vapour lamps will _not_ work.
Once the lens is apart it must be very thoroughly cleaned.
Recementing is done by putting a drop of cement in the center of the
convex surface and pressing the lenses together while gently moving
them with a circular sliding motion until the cement is evened out and
the excess is forced out the edges. Usually, the lens cell can be
used to keep the elements in alignment. The edges must be very
precisely aligned to preserve the centering. Any excess cement needs
to be cleaned off the edges. When Canada Balsam is used the elements
need to be put under gentle pressure and baked at somewhere around
150F for several hours to cure. The time depends on the hardness of
the Balsam. These days Balsam is available in liquid form which needs
to be allowed to dry out somewhat before using for lens cementing.
When UV cement is used it will set very quickly on exposure to the
curing light. This cement is _much_ harder to get apart than Balsam.
Cementing lenses isn't too diffucult for simple lenses but I would
suggest practicing on junkers before trying it on anything valuable.
The feathery looking separations in lenses are not always caused by
fungus, sometimes its just the cement crystalizing due to exposure to
excessive heat or cold.
Balsam seems to have been used as late as the late 1950's or later
by some manufacturers.
Thermo-setting cement will also separate sometimes. It often looks
like big bubbles trapped between the elements (which is just what you
are seeing). I've encountered this on some Wollensak lenses and seen
it on some Zeiss lenses which I think were probably subject so abuse.
---
From: "skgrimes" skgrimes@ma.ultranet.com
Ultraviolet curing cement (which will cure in any kind of UV lite including
sunlight) is available from Summers Optical
"UV-69" is available in 4oz bottles at around $25.00
1-800-523-5874
Old balsam lenses are separated by warming them to melt the cement (to about
250-300 degrees F) sliding the glass apart, cooling and cleaning with
acetone.
And, as the old British motorcycle manuals say "Assembly is simply the
reverse" SKG
From: dickburk@ix.netcom.com (Richard Knoppow)
Centering is done at the time of manufacture. The lens blanks are
lapped on machines which do many lenses at once. Lenses to be
cemented must have their surfaces done one at a time (one on a block)
so that they exactly match.
Once the lens is lapped and pollished it must be centered so that
the edge is both concentric and coaxial with the optical axis.
The old method of doing this was to mount the lens on a hollow tube
using soft cement so that the blank could be moved around. The lens
was rotated and the image of a point source observed through a
telescope. The lens was adjusted until the image of the reflection
of the point was still. When this was true for both surfaces the lens
was ground down to the right diameter for the mounting around the
center established this way.
If the lens wasn't centered correctly when it was made fixing it may
be very difficult since it means re-grinding the edges to get them
concentric. Sinc that makes them smaller the lenses must be
re-mounted. Hardly worth the trouble.
If a correctly centered lens must be re-cemented the elements must
be retured exactly to their original positions. Usually, this will be
established by the cell, or some other method of making sure that the
edges are exactly lined up all around.
Where elements of differing sizes must be cemented, as with an
Angulon, for instance, some form of fixture must be set up to make
sure the elements are exactly concentric and stay that way while the
cement sets.
About the only detailed information I've seen on the actual
techniques of lens manufacture were in an old book published in
England. I believe the title is _Optical Shop Practice_ but I can't
remember the publisher at the moment:-( It was a manufacturer of
optical manufacturing equipment. The book ran several editions, the
latest the LA library has is around 1955.
The only other source I've seen was in published intelligence reports
of German optical plants gathered after WW-2 by teams of the British
and American goverments. These are very difficult to find. The LA
public library has a very small collection which describe machinery at
the Zeiss plants at Jena and, if I recollect rightly, Dresden. There
is also a long report on the Shott Glass Works in Jena listing glass
types and some manufacturing techniques.
These reports covered all German industry and are the source of some
interesting formerly proprietary processes and techniques.
---
From: dickburk@ix.netcom.com (Richard Knoppow)
rmurai@oro.net (ricm) wrote:
It would be interesting to know which types these were and how old.
Are they current production or older lenses? If older its possible
that Rodenstock may have had problems with cementing at some time. I
don't know when Rodenstock switched to synthetic cements. Schneider
evidently used Canada Balsam up to the late 1950's. The use of a
synthetic cement does not guarantee against separation, I've seen a
number of mid-60's lenses which have either come apart or have
developed hazy cement. Some of the early thermo-setting cements could
definitely have problems. Modern cements are either low-temperature
curing or Ultra-Violet curing so don't develop the strains of some
earlier cements.
---
From: kirkfry@msn.com
I have two Rodenstock Sironar (single coated) f5.6 plasmat lenses, a 150mm
and 210mm, that were most likely manufactured in the 1960's that have
edge/more serious separations. I would be interested in how many other folks
out there are having this problem also with Rodenstock lenes. I own three
Schneiders, a Nikkor, a Goerz, three Fujinons, and two Ziess large format
lenes and none of these have shown any problems with separations.
Kirk Fry kirkfry@msn.com
From: Linda A Whatley linda_aw@ix.netcom.com
The balsam used to prepare microscope slides is a convenient
cement for lenses-- used as is, liquid at room temperature.
Does anyone have actual experience that the job is a good,
permanant one? or not?
Grimes' web page has a fine show and tell about getting a
lens group out of a burnished-over cell, by the way:
(http://www.skgrimes/burnish/index.htm).
- Larry Whatley
From: dickburk@ix.netcom.com (Richard Knoppow)
I've used liquid balsam a couple of times because there was no solid
type available. Its permanent. The liquid type balsam needs to be
allowed to dry out before use. The conventional balsam comes as a
solid which is melted into place onto a warmed lens. Once the cement
is distributed between the lenses they need to be left in a luke warm
oven for several hours.
Steve has a link on his web page to Summers Optical who sells
several types of modern optical cement. One type (type F-65) is a
binary cement for experimental or short run use which looks like a
better bet than balsam. I am about to order some to use on an old
Wollensak copy of a Protar. This stuff cures at room temperature.
Sets in an hour and is completely cured in three days. They also have
UV curing cements including some which cure with an ordinary sun lamp.
These cure faster than the binary type but the extra curing time is
actually an advantage if you are new to this.
The Summers Optical site also has pretty complete instructions for
cementing lenses. It covers both binary and UV curing cements.
These cements are easier to use than Canada Balsam. The elements do
not have to be heated and the cement does not need to be baked to
cure.
They are at:
---
rec.photo.equipment.large-format
bodyphoto@aol.comNOJUNK (BodyPhoto) wrote:
Missed this earlier. Hi Storm, The notches are for a spanner. You
can get big ones from Calumet for udoing shutter mounting flanges. A
better way of undoing lens retaining rings is to use a washer of soft
rubber, sticky latex is ideal, which is cut to fit the ring. It is
then turned with a cylindrical tool the right size. For small lenses a
bottle cap will work. For a larger lens you might try a jar cap. These
rings are sometimes hard to get off because some paint has gotten on
the threads. A few drops, and I mean only drops, of a solvent like
Acetone carefully run into the threads will help loosten it. Be very
careful not to get the solvent on the paint or let very much of it get
into the lens.
---
rec.photo.equipment.large-format
These rings can generally be removed without a tool. Use rubber "friction"
tools such as rubber stoppers, "o" rings, automotive inner tube, etc cut to
fit the ring and then turned with an appropriate size cylinder, such as a
tin can or coffee cup. A little solvent in the thread and a light touch
will usually get the ring turning. I never use a "spanner wrench" except as
a last resort. These wrenches are usually not necessary; using them can
easily result in the scratches and "worrying out" of the slots which is so
commonly seen. There is a picture of a typical spanner wrench being
auctioned at the moment (don't worry about it being the only one, this guy
seems to auction these a lot)
http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item;=45527983
--
rec.photo.equipment.large-format
A really useful piece of info given that I have a collection of old
cameras/lenses many of which require real good clean up.
A follow-on question is:- how do you deal with lenses which have a
slight ding on the threads which make the retaining ring hard to
turn?
"skgrimes" skgrimes@ma.ultranet.com writes:
rec.photo.equipment.large-format
You have to straighten the ding first. This can be done using a variant of
the technique shown at: http://www.skgrimes.com\popsci\burnish\index.htm
specifically the split ring shown in the first "series" picture. Make such
a ring to fit the dented lens, clamp the lens firmly into it using a
hose-clamp, three jaw chuck, or plain bench vise then use an end grain
wooden punch to coax the ring against the shape of the split ring. This can
often be done with no damage to the threads. Attempting to straighten the
rim without a perfectly and tight fitting "receiver" for the straightening
will probably spoil the job.
rec.photo.equipment.large-format
Dick Streff ds85035@navix.net wrote:
I simply don't know about this stuff. Summers Optical offeres
several types of optical cement, both UV curing and binary (two
component) types. I've used the standard binary cement with some
success. It cures at 150F. There is also a room temperture curing
cement but I prefer the longer set-up time available with the heat
curing type. I use the kitchen oven for curing. Temperature is not
very critical. The cement will cure at room temperature but takes
several days. At 140deg it takes about one hour total.
UV cement requires a UV source. Summers claims their stuff will cure
with a sunlamp. The UV sources sold by Edmund for this purpose are
outrageously expensive.
The problem with Summers Optical cements is that they must be
shipped as hazardous materials which just about doubles the price.
Summers also has a good tutorial on lens cementing on their web
page. http://www.emsdiasum.com/Summers/optical/cements/default.html
Getting lenses cemented with synthetic cements apart once glued can
be a problem. Summers offeres a de-cementing solvent which must be
used at 340F. The lens is immersed in this stuff and placed on an
electric frying pan or similar flameless heater. It takes a few
minutes for the elements to separate. It is just as well to order the
de-cementing solvent along with the cement since it will save a
separate hazardous materials charge and you will need it if you goof.
(I have).
Lenses can be cemented the old-fashioned way with Canada Balsam but
it is a pain to use especially for more than a single surface.
The Summers glue works fine. You will need to be careful of clamping
to insure the element edges are exactly lined up. I use a small sheet
of plate glass for the flat surface and right-angle metal blocks to
hole the edges of the lens. The blocks must be exactly 90deg. The ones
I use were made for clamping large ground wires in electrical
installations. I was surprized at how accurate the right angle is.
As far as the Dagor, if you are going to re-cement the front element
you might as well go all the way and re-cement the whole lens.
Canada Balsam will unstick with gentle heating. I've found that
immersing the lens in water and heating it is gentler than trying to
heat the lenses on a frying pan, wich is the traditional way. At some
point the Balsam becomes milky and lenses just fall apart.
Do one surface at a time and let it set-up (20 minutes in the oven
for the Summers stuff I mentioned) and then do the next.
For the edge paint the best stuff available right now is Krylon
Ultra-Flat Black. This is available in spray cans from hardware
stores. It is a _very_ matt black surface. You can brush it on by
spraying some into a small container. This material out gasses as it
drys so its a good idea to bake it after coating. The same oven can be
used. It takes about half an hour at 130F to cure the stuff. Without
baking I would wait a couple of days before re-assembling the lens.
This is probabaly not a big deal for a Dagor since all air surfaces
are exposed for cleaning but it may be important when painting edges
of elements which are going to be sealed in a cell. The stuff from the
paint will eventually cause a haze on the glass surface which will
have to be cleaned off. This seems to happen to very old lenses
anyway.
Lens cementing is an interesting adventure and not as difficult as
sometimes made out.
Most lenses will center automatically when the edges are matched.
There are a few, like the Schneider Angulon, which have elements of
different sizes cemented together, which need more elaborate methods
of centering than just simple edge clamping. The method has to be
worked out for each lens. "Centering" of the elements is done as part
of the manufacturing process. The edges of the polished lenses are
gound concentric and coaxial with the optical center of the lens. Once
done that doesn't change.
Good luck and have fun:-)
---
rec.photo.equipment.large-format
The UV cements are very difficult to un-do. They require over 350 degrees
F heat to get them to fail and separate. Summers Optical (see my link
list) advertises a product called "Milbond" along with a "Milbond solvent"
I have no experience with this. They also sell a furyl alcohol "lens
decementing agent" which is highly flammable, seems really toxic and is a
total pain to use, but it does work and separates otherwise impossible to
separate lenses. The internal ( big minus lens) in Dagors must be cooled
very slowly (overnight, wrapped in a thick dry towel) after separating,
cooling too rapidly may cause it to crack and be spoiled. I use Summers
"UV 69 " and make sure it is really right before applying the UV cure.
The good news is that it you get it really right before applying the cure
then you don't have to do it again for another two or three hundred years.
See: http://www.skgrimes.com/popsci/index.htm for
info and pictures about lens cementing.
--
rec.photo.equipment.large-format
Just an update on this particular cement. My package from Micro-Tools came
today. The cement in question is actually an off the shelf product from Duro,
a subsidiary of the Loctice Corporation of threadlocker fame. It appears from
the illustration on the front of the blister package that its intended
use is
for repairing broken household glassware. Micro-Tools has stapled a
needle tip
on the package as an add on.
I don't know as I'm willing to risk this particular Dagor to experiment,
so I
went ahead and ordered some UV-74 directly from Summers Laboratories this
morning. It was actually $2.50 a bottle less ordering direct from Summers as
opposed to buying through Edmund Scientific.
I do have some less critical (read valuable) lenses that maybe I'll
experiment
on with the Micro-Tools cement. I'd be interested in seeing if the cheap
stuff
doesn't actually perform as well as Summer's stuff. I'll report back any
findings when I do so.
Thanks again to everybody for their input.
Dick Streff
[Ed. note: for your info, caveat repairer!]
To repair the rear lens group whereby the cement had failed between two
elements of this group, I used the following procedure:
1. Separated two lens with 350 F heat in an oven. Fifteen minutes in a
preheated oven was more than needed. The lens slid apart.
2. Cleaned lens elements with methanol-based lacquer thinner and lint free
wipes purchased at an electronics supply store.
3. Chose balsam canada, purchased from Post Apple Scientific for $19.
delivered, as the glue (novice friendly).
4. Applied one small drop in center of convex lens top. Placed other lens
on top and smashed and swirled until dispersed. This glue is really sticky
and somewhat OPAQUE....surprise!
5. These lens are the same diameter so I placed and tightened a relatively
wide "cable strap/tie" (those plastic strips used to cinch wires) about
them to hold the lens perfectly centered.
6. After cleaning away excess glue with thinner, I used a very light-weight
C clamp with thick FELT pads at the centered, lens contact points to apply
pressure to the bond. The clamp is one I use to mend guitar tops.
7. Cooked clamped and strapped lens in a preheated 175-200 F oven for six
hours.
8. Removed and let cool for two hours. Carefully cut strap/tie off with an
exacto knife and removed felt-tipped clamp.
9. Cleaned lens again with thinner and lint-free pads.
10. Observed excellent centering of lens and also, that the glue had dried
perfectly clear. (surprise again!)
11. Installed elements and fixed myself a deserved rum and cola.
Anyhoooo. One can do this stuff with a few tools and a lot of common sense.
ron james
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Cementing Lenses
Date: Wed, 8 Apr 1998
From: Todd Belcher toddmb@intergate.bc.ca
To: rollei@mejac.palo-alto.ca.us
Subject: [Rollei] Rollei 2.8 Planar
From: Richard Knoppow dickburk@ix.netcom.com
To: rollei@mejac.palo-alto.ca.us
Subject: Re: [Rollei] Removing & Disassembling TLR viewing lens
At 06:27 AM 4/19/98 -0700, you wrote:
>I picked up a Rolleicord IV yesterday. It had slight fungus in both taking
>and viewing lens. (it's a "user" not a collector.)
>
>I had no trouble removing the taking lens with a rubber plug and cleaning
>it. I can move the viewing lens slightly with the rubber plug, but it
>seems to be more difficult to remove. And, I don't see any "notches" in
>the front retaining ring to use a spanner. What's the trick to opening the
>viewing lens for cleaning?
>
>
>
> bob...
Richard Knoppow
Los Angeles,Ca.
dickburk@ix.netcom.com
From: Peter Klosky PKlosky@bdm.com
To: hasselblad@kelvin.net
Subject: flat black application for lenses
Has anyone on the list found a need to disassemble their lenses and
paint the cases flat black? I was reading recently that certain lenses, in
specific the Kiev lenses for the old Hasselblad, benefir from this
treatment. Anyone have practical experience in this area?
From: " Dante A. Stella" dante@umich.edu
To: rollei@mejac.palo-alto.ca.us
Subject: Re: [Rollei] Recementing lenses
On Mon, 27 Apr 1998, JJMcF wrote:
> Todd's post was extremely interesting and potentially valuable. If the
> elements are cemented with canada balsam, can you use a solvent less nasty
> than methylene chloride? (I've got a couple of old Tessars with separated
> rear elements).
> John McFadden
>
From: Todd Belcher toddmb@intergate.bc.ca
To: rollei@mejac.palo-alto.ca.us
Subject: Re: [Rollei] Recementing lenses
From: "Kotsinadelis, Peter" Peter.Kotsinadelis@octel.com
Reply to: rollei@mejac.palo-alto.ca.us
Subject: [Rollei] RE: Lens cleaning
While acetone may be a good solution, the side effects are far
too serious (acetone can damage paint, dissolve cement, etc.).
Many current manufacturers use AMethyl Ehtyl Alcohol to clean
optical lenses. This is used by Tokina and many others.
This alcohol is not readily available, however, Photographic
Solutions offers Crystal Clear which is a 99.99% pure alcohol
that is relatively safe and evaporates without any residue.
Call them 1.508.759.2322
Incidentally, items like windex and other ammmonia compounds
contain water. Water will destroy the coating on a lens over
time. Use these solutions only if you have aspheric elements
made of plastic (some lenses incorporate molded aspherical
elements). Otherwise, try Crystal Clear.
Peter K
From: Richard Knoppow dickburk@ix.netcom.com
To: rollei@mejac.palo-alto.ca.us
Subject: Re: [Rollei] Recementing lenses
At 03:53 PM 4/28/98 EDT, you wrote:
>Many thanks to Todd and Richard for their information on this subject. A
>couple of armchair questions that occur to me before descending into my
>laboratory (emphasis on second syllable) to decement my precious optics with
>toxic substances: (1) can you substitute one cement for another, considering
>that different cements must have different refractive coefficients? and (2)
>does the thickness of the cement layer have any optical significance either in
>practice or in theory? If so, how is that thickness controlled in the
>recementing process? Finally, (rhetorical question) why is it that the lenses
>with the worst separation problems are among your best lenses, rather than
>junkers that you don't mind working on?
>John McFadden
>
Richard Knoppow
Los Angeles,Ca.
dickburk@ix.netcom.com
From: Todd Belcher toddmb@intergate.bc.ca
Subject: Re: [Rollei] Recementing lenses
From: " Dante A. Stella" dante@umich.edu
Subject: Re: [Rollei] Recementing lenses
From: Tony Zoccolillo tzoc@servtech.com
Subject: RE: [Rollei] SL35 series lenses - how to disassemble?
Tony Zoccolillo
From: JJMcF JJMcF@aol.com
Subject: Re: [Rollei] Swapping lenses and lens groups
From: Richard Knoppow dickburk@ix.netcom.com
To: rollei@mejac.palo-alto.ca.us
Subject: Re: [Rollei] Recementing lenses
At 08:03 PM 4/27/98 -0800, you wrote:
>John,
>
>Yes. If Canada Balsam is the cement of choice, then Methyl Hydrate can be
>used to unglue the elements. A step up from that would be Acetone, then the
>methylene chloride. Methyl ethyl acetone will also work, but I think that
>it is going to be placed on the hazardous chemical list.
>
>>From experience...and no Zeiss data...it appears that Zeiss was using
>synthetic glues for their lenses in the early 50s, yet at the same time and
>for years to come they used Canadian Balsam. An example are the Contaflex
>accessory lenses from the 60s and early 70s which appear to be glued with
>Canada Balsam, yet the 2.8 Planars from the early/mid 50s earlier appear to
>be glued with a synthetic as they are much more difficult to unglue. The
>Tele Rolleis appear to use the same synthetic glue.
>
>Try the Methyl Hydrate on the old Tessars. If they come apart overnight or
>in a day or two...it's Canada Balsam. If not successful try acetone...then
>the Methylene chloride. At this point it is sure to be the synthetic glue.
>
>
>
>todd
>
>
>>Todd's post was extremely interesting and potentially valuable. If the
>>elements are cemented with canada balsam, can you use a solvent less nasty
>>than methylene chloride? (I've got a couple of old Tessars with separated
>>rear elements).
>>John McFadden
Richard Knoppow
Los Angeles,Ca.
dickburk@ix.netcom.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: HELP: Lubricating older cameras
Date: 1 May 1998
>them apart. Any ideas on the type of grease to use? Lighter fluid
>cleaned them up but I think I need something thicker. I am now
>recalibrating the focus and would like to finish this project and start
>
Cees de Groot http://pobox.com/~cg
Newsgroups: rec.photo.equipment.large-format
Subject: Re: HELP: Lubricating older cameras
Date: Fri, 1 May 1998
--Machine work for photographers
--Lenses fitted to shutters, iris scales engraved
http://www.skgrimes.com
Date: Fri May 01
21:51:45 CDT 1998
From: ELYOD SAMOHT gdthomas@pacifier.com
[1] Re:
HELP: Lubricating older cameras
> > I
recently purchased two post war European medium format folding > cameras.
They are both extremely compact and cute. To focus these > cameras the
lens mount holding the front element rotates inside a > housing which then
screws into the shutter. The grease in the threads of > these mounts had
turned to glue and it took considerable effort to get > them apart. Any
ideas on the type of grease to use? Lighter fluid > cleaned them up but I
think I need something thicker. I am now > recalibrating the focus and
would like to finish this project and start > shooting. > Thanks, Craig
Wester
Date: Fri May 01 21:51:45 CDT 1998
From: ELYOD SAMOHT gdthomas@pacifier.com
[1] Re: HELP: Lubricating older cameras
>
> I recently purchased two post war European medium format folding
> cameras. They are both extremely compact and cute. To focus these
> cameras the lens mount holding the front element rotates inside a
> housing which then screws into the shutter. The grease in the threads of
> these mounts had turned to glue and it took considerable effort to get
> them apart. Any ideas on the type of grease to use? Lighter fluid
> cleaned them up but I think I need something thicker. I am now
> recalibrating the focus and would like to finish this project and start
> shooting.
> Thanks, Craig Wester
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Cementing Lenses
Date: Wed, 01 Apr 1998
Richard Knoppow
Los Angeles, Ca.
dickburk@ix.netcom.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Re:Cementing Lenses
Date: Wed, 1 Apr 1998
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Cementing Lenses
Date: Sat, 04 Apr 1998
Richard Knoppow
Los Angeles, Ca.
dickburk@ix.netcom.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Element Separation in Rodenstock Lenses?
Date: Sun, 24 May 1998
>I've seen an inordinate number of Rodenstock LF and
>enlarging lenses with separation in the elements.
>
>Perhaps this is totally coincidental but has anyone
>else noticed this?
>
>Rick Murai
Richard Knoppow
Los Angeles, Ca.
dickburk@ix.netcom.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Element Separation in Rodenstock Lenses?
Date: Sun, 24 May 1998
Newsgroups: rec.photo.equipment.large-format
Subject: Cementing Lenses
Date: Fri, 19 Jun 1998
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Cementing Lenses
Date: Fri, 19 Jun 1998
http://www.emsdiasum.com/Summers/optical/cements/default.html
Richard Knoppow
Los Angeles, Ca.
dickburk@ix.netcom.com
From: dickburk@ix.netcom.com (Richard Knoppow)
[1] Re: Unscrewing lens rings
Date: Sun Nov 29 05:05:59 CST 1998
>I have a telephoto lens for my Speed Graphic which has mildew between the lens
>elements. I can see the two small nothes opposite each other which should
>allow me some leverage to dissasemle the lens for cleaning, but I can't find a
>tool to fit into the notches. Any suggestions would be appreciated. Please
>email to storm@stormjenkins.com
>Storm Jenkins, Photographer
>Los Angeles - San Francisco
>www.stormjenkins.com
Richard Knoppow
Los Angeles, Ca.
dickburk@ix.netcom.com
From: "skgrimes" skgrimes@ma.ultranet.com
[1] Re: Unscrewing lens rings
Date: Sun Nov 29 15:38:53 CST 1998
--- S.K. Grimes -- Feinmechanik ----
From: mpaton@hpqs0116.sqf.hp.com (Mike Paton)
[1] Re: Unscrewing lens rings
Date: Mon Nov 30 09:31:33 CST 1998
>These rings can generally be removed without a tool. Use rubber "friction"
>tools such as rubber stoppers, "o" rings, automotive inner tube, etc cut to
>fit the ring and then turned with an appropriate size cylinder, such as a
>tin can or coffee cup. A little solvent in the thread and a light touch
>will usually get the ring turning.
From: "skgrimes" skgrimes@ma.ultranet.com
[1] Re: Unscrewing lens rings
Date: Mon Nov 30 20:41:29 CST 1998
From: dickburk@ix.netcom.com (Richard Knoppow)
[1] Re: Lens Cement
Date: Sat Mar 20 16:07:07 CST 1999
>I've been doing some research on cementing lenses and found several posts on
>the subject. I have ordered cement from Micro-Tools as they have it for $4.00
>(I believe it's a pretty small quantity). The brand name is "Crystal Clear".
>The catalog description says it's a "UV cure glue for re-cementing lens
>elements together".
>
>I'm reluctant to pay the $20+ and $7 minimum shipping that others (notably
>Edmund Scientific) want for their cements. I probably wouldn't be able to use
>it up fast enough unless it has a long shelf life.
>
>Do anyone know any specific reason I should avoid this cheaper stuff? I've got
>the front element of the Dagor I previously posted about uncemented and
>cleaned, so any advice on adhesives I could get would be appreciated. Since
>this is my first time at this, I'd like to use a cement that is potentially
>reversible just in case. I know all the new cements are more difficult to undo
>than Canadian Balsam, but I don't want to use something to incredibly
>difficult to remove.
>
>Thanks
Richard Knoppow
Los Angeles, Ca.
dickburk@ix.netcom.com
From: "skgrimes" skgrimes@ma.ultranet.com
[1] Re: Lens Cement
Date: Sat Mar 20 18:16:09 CST 1999
--- S.K. Grimes -- Feinmechanik ----
From: Dick Streff ds85035@navix.net
[1] Re: Lens Cement
Date: Tue Mar 23 15:25:46 CST 1999
Date: Sat, 22 May 1999
To: bronica@iList.net
From: ron james studior@ionet.net
Subject: [BRONICA] ETRs MC 75mm/2.8 lens cementing project