Related Links:
Wallace ExpoDisc Pages (Pre-flashing tool) were at http://www.expodisc.com/desc.html
[Ed. note: I was sorry to hear that Mr. Wallace has passed away.. [4/2002]]
Pre fogging or pre-exposure to reduce contrast
Post-Exposure Flashing Technique
Email suggestions, updates, comments, links, and glitches to fix - Thanks!

[Editor's Notes:

Pre-flashing film and film hypering are two methods to alter the characteristics of film to achieve greater sensitivity and desired properties.

Elyod Samoht describes his pre-flashing technique in the posting below.

For more on film hypering or film hypersensitization, see the various astrophotography newsgroup and websites that deal with film gas-based hypering. This process exposes film to high pressures of inert gases which reportedly cause the film to swell and otherwise alter its characteristics. The major gain is a large decrease in reciprocity failure due to long exposures (hence, shorter exposures) with minimal changes in grain or color shifts with the film emulsion.

There are also some post-exposure techniques, such as exposure to hydrogen peroxide fumes and other less popular techniques, which are supposed to provide faster film sensitivity after exposure. These processes seem less popular (and more doubtful) but then, I haven't tried them ;-).

These techniques are completely separate from the push-processing usually used to change development times so as to enable a film to be exposed with less light (as if a higher ASA figure applied). Again, many photographers have expresses surprise at the quality of push-processing on some of the newer color films at 800 ASA to 1600 ASA and above ratings.

Note that pre-flashing may still have a role to play, because it impacts shadow areas differently from highlights, so may meet various special needs.

Date: Sun, 21 Jun 1998
From: ELYOD SAMOHT gdthomas@pacifier.com
Organization: PRIMARY FOCUS PHOTOGRAPHY

pre flashing works using the Law of Diminishing Returns. Pre exposure "charges" the total film surface. At the time of exposure in the shadow areas fewer grains are light struck that in the high lights so the pre charge causes more grains to reach the threshold of detail. In the high lights most of the grains are light struck anyway so there is less effect. Pre flashing can buy you 1/2 stop in the shadows at the cost of 1/4 stop in the high lights (app..)

Here is how I do it. The camera is set up normally and the light meter is set to your normal ISO. Determine the desired settings for f-stop and shutter speed. Increase the shutter speed by three stops (trans film) and place a piece of white glass (available at most glass shops) flat on the lens and trip the shutter. Reset the speed and shutter and expose normally. It works!

PRIMARY FOCUS PHOTOGRAPHY

Anyone wrote:

> Does anyone have some experiences they could share on the technique used
> to soften the contrast of films before taking a shot. Do you use a white
> card on location, pre-expose before going out, exposure levels, metering
> etc?
>
> I am shooting 4X5 transparencies of waterfall scenes in a deep canyon  
> area. The basalt rocks are quite dark (almost black) and covered with
> greenery. Many of the scenes look best when the sun is relatively high
> (due to the depth of the canyons) and the foreground tress are back lit.
> This leaves the are behind the fall in the deep shadows with nice
> highlights on the waterfall. When the sun is low the scenes go flat and
> loose their 3 dimensional look (since no direct light is entering the
> canyon).
>
> The bottom line is some of these scenes tend to be high contrast (5-6
> stops dynamic range). I received some good metering tips from a local
> outdoor photographer (thanks Don), but there is still to much contrast
> in some of the scenes which push the film just a little to far outside
> it's dynamic range. The transparencies look pretty nice but are still
> not quite right.
>
> I am using fuji Provia and Velvia. Metering with a Weston Master (for
> averaging)  and Sekonic L-508 (for spot).     
>
> Direct replies should be to:
> dpayne at pacifier dot com
>
> Thanks,
>
> Dave  

From: "Michael K. Davis" zilch0@primenet.com
Newsgroups: rec.photo.equipment.large-format
Subject: Re: Pre-Exposure softening
Date: 1 Jul 1998

The Wallace Expo/Disc is perhaps the best tool available for pre-flashing, not to mention converting any TTL-metering camera into an incident meter, and he's practically giving them away -- I think they are a great value, anyway.

See it at:

http://www.expodisc.com/desc.html

If you want to know everything there is to know about pre-flashing, call George Wallace at (408) 778-2040. He is a teacher and loves to share. I called just to place an order and got much more, to my benefit.

Brian Ellis beellis@gte.net wrote:
: Ansel Adam's book "The Negative" contains a good discussion of pre-flashing.
: It can be done at home or in the field. You use a diffuser of some type. 
: Adams' book discusses one that can be home made. Brian

: Anyone wrote:

: > Does anyone have some experiences they could share on the technique used
: > to soften the contrast of films before taking a shot. Do you use a white
: > card on location, pre-expose before going out, exposure levels, metering
: > etc?
: >
: > I am shooting 4X5 transparencies of waterfall scenes in a deep canyon
: > area. The basalt rocks are quite dark (almost black) and covered with
: > greenery. Many of the scenes look best when the sun is relatively high
: > (due to the depth of the canyons) and the foreground tress are back lit.
: > This leaves the are behind the fall in the deep shadows with nice
: > highlights on the waterfall. When the sun is low the scenes go flat and
: > loose their 3 dimensional look (since no direct light is entering the
: > canyon). 
: >
: > The bottom line is some of these scenes tend to be high contrast (5-6
: > stops dynamic range). I received some good metering tips from a local
: > outdoor photographer (thanks Don), but there is still to much contrast
: > in some of the scenes which push the film just a little to far outside
: > it's dynamic range. The transparencies look pretty nice but are still
: > not quite right.
: >
: > I am using fuji Provia and Velvia. Metering with a Weston Master (for
: > averaging)  and Sekonic L-508 (for spot).
: >
: > Direct replies should be to:
: > dpayne at pacifier dot com
: >
: > Thanks,
: >
: > Dave  

--
/---------------------\
Michael K. Davis
zilch0@primenet.com
MIME Attachments OK
\---------------------/

From: David Bindle bindle@sklib.usask.ca
Newsgroups: rec.photo.equipment.35mm
Subject: Preflashing film to reduce contrast.
Date: Tue, 9 Feb 1999

I'm thinking about experimenting with preflashing (via double exposure) to reduce contrast. (In extremely high contrast situations)

I'm not sure if I am thinking of the right reasons and methods for doing this, so please set me on the right track if I am wrong.

First... we need a situation to photograph. Let's say I'm trying to make the best of a bad situation.

Sunny day... no shade, couple in dark suit and light dress, and I have a fairly high contrast film. (Royal gold 100... Velvia, etc...) Now, (aside from using fill flash...or, as well as...) could I use the double exposure feature to:

... make an exposure of an out of focus grey card at, say, -3 stops, then shoot the couple at the proper exposure, and expect that my resulting image will have more details in the blacks as well as the highlights?

Is this a practical application of preflashing a frame of film? I also have an Elan IIe and it has very accurate film hole registration when inserting a previously shot, but half unused film.

Could I preflash (frame by frame) a whole roll of Velvia or Royal Gold 100 (or whatever) to reinsert at a later date and expect to get the qualities (or at least some of the qualities...) of more expensive, lower contrast, professional portrait films?

If I'm all wrong on this... could someone point me to a website that explains preflashing or prefogging film?

Thanks

David Bindle

From: "Michael K. Davis" zilch0@primenet.com
Newsgroups: rec.photo.equipment.35mm
Subject: Re: Preflashing film to reduce contrast.
Date: 9 Feb 1999

Hi!

David Bindle bindle@sklib.usask.ca wrote:

: I'm thinking about experimenting with preflashing (via double exposure) to
: reduce contrast. (In extremely high contrast situations)
:
: David Bindle

The Wallace Expo/Disc is perhaps the best tool available for pre-flashing, not to mention converting any TTL-metering camera into an incident meter, and he's practically giving them away -- I think they are a great value, anyway.

See it at:

http://www.expodisc.com/desc.html

If you want to know everything there is to know about pre-flashing, call George Wallace at (408) 778-2040. He is a teacher and loves to share. I called just to place an order and got much more, to my benefit.

Mike Davis

--

Newsgroups: rec.photo.technique.misc
Subject: Re: Preflashing film for contrast control
From: ddb@ddb.com (David Dyer-Bennet)
Date: 9 Feb 99

David Bindle bindle@sklib.usask.ca writes:

>I'm thinking about experimenting with preflashing (via double
>exposure) to reduce contrast. (In extremely high contrast situations)
>
>I'm not sure if I am thinking of the right reasons and methods for
>doing this, so please set me on the right track if I am wrong.

I haven't used this technique myself, but it's in the book (various books I own, anyway). I've talked to some motion picture photographers who have actually used it, and think reasonably well of it.

>First... we need a theoretical situation to photograph. Let's say I'm
>trying to make the best of a bad situation. For example...  
>Sunny day... no shade, a couple with one in dark suit and the other in a
>light dress, and I happen to be stuck with a fairly high contrast film.
>(Royal gold 100... Velvia, etc...)
>
>Now, (aside from using fill flash...or, as well as...) could I use the
>double exposure feature to:
>
>   ... make an exposure of an out of focus grey card at, say, -3 stops,
>then shoot the 2nd exposure of the same frame of the couple at the
>proper exposure, and expect that my resulting image will have more
>details in the blacks as well as the highlights?
>
>   Is this a practical application of preflashing a single frame of
>film?

Yes, this is the right idea. -3 stops isn't crazy, but I don't remember what the canonical suggestion is. -3 stops puts the middle greys at zone 2, meaning nothing will be darker than zone 2 in the entire picture. Maybe that's a stop too much pre-flash; but as I say, I don't remember the canonical way to do this, I only remember the general principal.

>I also have an Elan IIe and it has very accurate film hole registration
>when inserting a previously shot, but half unused film, so...
>
>Could I preflash (frame by frame) a whole roll of Velvia or Royal
>Gold 100 (or whatever) to reinsert at a later date and expect to get
>the qualities (or at least some of the qualities...)  of more
>expensive, lower contrast, professional portrait film?

There are tradeoffs in the quality still. As to whether counting on the registration would work -- depends how good the registration is. If it's always in the same sprocket hole, I'd think it was worth a try, myself.

--
David Dyer-Bennet ddb@ddb.com
http://www.ddb.com/~ddb (photos, sf)

From: delfstrom@usa.net (David Elfstrom)
Newsgroups: rec.photo.technique.misc
Subject: Re: Preflashing film for contrast control
Date: Wed, 10 Feb 1999

bindle@sklib.usask.ca wrote:

>I'm thinking about experimenting with preflashing (via double exposure)
>to reduce contrast. (In extremely high contrast situations)
>I'm not sure if I am thinking of the right reasons and methods for
>doing this, so please set me on the right track if I am wrong.

Read it from the master himself, Ansel Adams, in his book "The Negative". For the odd time when I need to reduce contrast, I've done an initial exposure through a translucent peice of white acrylic (like what light tables/boxes are made out of), at -3 stops, and using the multiple exposure feature of the camera take the real scene as you normally would. This technique doesn't decrease contrast, it basically boosts the deepest zone from no detail up to some detail. Ansel Adams describes it very well in his book. I know you want a website, but even websites dedicated to the Zone System of photography still point the reader to his books first, before asking questions.

DavidE.

From: "Rich" rich@utahshooter.com
Newsgroups: rec.photo.technique.misc
Subject: Re: Preflashing film for contrast control
Date: Sun, 14 Feb 1999

I use a preflash when duping slides and making internegs. It does a better job than any slide duping or interneg film. Without seeing the original, it's hard see it's a dupe.

To make it easy, I shoot my preflash through a Kodak No. 96 gelatin filter (N.D. 2.00). That way, I don't have to play with f-stops. Besides, it's hard to do -3 stops if you are already at f-16.

Rich
http://www.utahshooter.com

[Ed. note: interesting idea, preflash in camera etc.]
From Leica List:
Date: Thu, 02 Mar 2000
From: Stephen Gandy leicanikon@earthlink.net
Subject: Re: [Leica] Ebay -- fact or fiction!

haven't got the camera yet. As I dimly recall from a Modern Photo article I have not been able to find, the LED pre-flash increased B/W film sensitivity 2-3 stops. Not sure how, or how well, it works in practice. I plan to do a future article on it.

Stephen Gandy

Jeremy Kime wrote:

> Bob,
> I was bidding on a weird 'user' M3 that had been converted, at some stage,
> to run with leds in the corner of the shutter case for hypersensitive
> pre-flashing of the film, or so I understood the explanation.
> However, some other guy comes along and snaps it from under my nose, and he
> a fellow Lugger to boot! Maybe we should invent some gentleman's rules
> here!! (only kidding...)
>
> How is that camera Stephen (Gandy)?
>
> best regards,
> Jem

From Rollei Mailing List:
Date: Fri, 28 Jan 2000
From: Jon Hart jonhart51@yahoo.com
Subject: Re: [Rollei] Diffuser?

--- bigler@jsbach.univ-fcomte.fr wrote:

> There is diffuser sold as a 35 mm SLR accessory
> (distributed in France
> by Contax) that allows you to get incident light
> readings with any
> "modern" 35 mm SLR light metering systems. You just
> screw the diffuser
> in front of any lens like a filter (e.g. 52 mm
> thread) and it catches
> incident light exactly like and invercone on a
> classical Weston meter.

There is or was such a device made here in the U.S. The name escapes me at the moment (very simple, at that). There is a procedure involved in taking a reading as well as a certain amount of calibrating with the device involving the making of a series of negatives with it over the lens at varying apertures until an 18% gray is achieved. Once this is done, you can, based on the previous tests, set the meter with the optimum EI and aim into the sky (or was it the sun?) and take a reading. This is about the extent of my memory on the subject. Perhaps someone else has used these before and can elaborate? Personally, I always wanted to get one but never did. Stooopid!! Now, I use an ancient Norwood Director with its various cones and flat diffusers. I will admit to being a meter heretic in my younger days, believing hat only the built-in meters were worth my trust. HAH!!!

Jon
from Deepinaharta, Georgia

Newsgroups: rec.photo.technique.misc
Date: Fri, 19 May 2000
From: cheungmo@mlink.net (Pierre Renault)
Subject: Re: Film Flashing Technique??? Anyone know how?????

> > I read about how some movies were made to look "faded" and "washed
> > out" by pre-exposing the film somehow. [...]
>
>There were lots of weird things that have been done to film regarding
>pre-exposure and post-exposure to light.  Sometime it caused
>"solarization," other times it (supposedly) hyper sensitized the film.

The general idea was to raise the threshold at which the film "noticed" it had been struck by light. It tends to add some detail in the shadows. The general effect flattens out the curve a little. You can try the concept out with paper and pencil.

>IMHO, the exact effect is unpredictable, as it depends on MANY
>variables. Try pre exposing the film before shooting, after shooting,
>etc with BRIEF amounts of weak light.

Flashing after exposure won't have the same effect as flashing before exposure because the threshhold effect doesn't come into play quite the same way.

Pre-flashing can be made repeatable by using a standardised setup and working consistently. One copy photographer I know used to pre-flash his copy film to get better rendition. He used a 4x5 camera set up on a small copy stand as his preflash camera for whenever he had to copy from photographs. The effect was quite good, though it did take him quite a bit of experimenting to get it right. Another used to pin his 35mm colour film up on wall and he had a small electronic flash permanently fixed to another wall about twenty feet away. The flash head had been nearly completely covered with electrical tape to lessen the output. Again, it took a bit of trial and error to get it right, but once he got it right, he left everything as it was; flashes being flashes, his results were quite consistent from roll to roll.

Getting back to the original question, I don't think the washed-out effect was achieved quite by following the standard pre-flashing techniques of the Forties. I have a feeling that the film was simply fogged by pre- or post- flashing a greater amount than usual to make it look old. You can always experiment yourself.

Pierre

From: Tony Spadaro aspadaroas@post.com
Date: Thu, 18 May 2000
Newsgroups: rec.photo.technique.misc
Subject: Re: Film Flashing Technique??? Anyone know how?????

Pre-flashing is used more to control high contrast. I don't like the look but it's a matter of taste. The directions I recall were to lay out the film, emulsion side up, in total darkness. Flash it for 1/10th second using a 15 watt bulb in a soup can with a 4 stop ND filter over the end. The bulb has to be high enough above the film to expose the entire roll - probably about 5 or 6 feet - and you have to make sure your shadow doesn't fall on it.

Now the bad news: I may have one or more of the directions messed up - it's been 25 years and I wasn't the one doing it, it was just a darkroom I shared.

And the good news: If you have a good library in town, or better yet a university library, look for an old book on photography, preferably one with a lot about News photography. Pre-flashing was either used a lot by the newspaper photographers of the 40s and 50s, or at least it was popular with photo book writers of the time

[Ed. note: the following information relates the use of the Wallace EXPO-DISK for ambient light metering with reflected light meters in most 35mm SLR cameras. The EXPO-DISK also has uses in preflashing etc..]

Date: Sat, 01 Jul 2000

Reply to: minolta-l@listserver.isc.rit.edu

• Then, if you note the number of "click-stops" involved and apply this same adjustment to the ISO rating of any film used in this particular camera, and with any lens

George Wallace

george@wallaceway.com

From: "Philippe Tempel" ptempel@home.com>
To: rollei@mejac.palo-alto.ca.us>
Subject: RE: [Rollei] A pre-exposure device
Date: Thu, 24 Jan 2002 

Jim, I was thinking of one like this:

http://www.zonesystem.com/toolkit/

click on the "building the diffuser" link.  It has
the following part list:

2 - 4 1/2"x 4 7/8" (11.5 cm x 12.5 cm)
pieces of white translucent plastic, about 1/8" (3 mm) thick 
3/8"x1/8" (9mmx3mm) acrylic rod cut into three pieces: 
2 pieces 4.5" (11.5 cm) long 
1 piece 4 1/8" (10.5 cm) long 
super glue or Plaststruct T 
masking tape 

So he seems to like a thicker (3mm) plastic.  The
thickness is probably not a big deal.  It was actually
from this site that I learned about this and that AA
had a similar device in his book.  I must have forgotten
about it because I have had AA books for at least ten
years.  Proving that they need to be revisited every
so often.  Or maybe that older age and/or selective
memory is kicking in? :-)

> I can get some of the plastic you require here in the north of Boston
> area.  I used some recently to make a large "viewer" for my 11x15
> chromes.
> 
> Let me know how much you want and the approximate thickness.
> 
> You might also want to try using the bottom(s) of a large plastic yogurt
> container.
> 
> 
> Jim
> 
> http://www.hemenway.com
> 
> 
> 
> Philippe Tempel wrote:
> > 
> > Anyone build one of these?  Its two pieces of
> > white plastic that's translucent enough to let
> > some light through.  You cut two small sheets
> > of them and three strips.  Then you bond the
> > sheets to the strips on three sides leaving a
> > pocket for ND gels.  Ansel Adams describes using
> > this in the pre-exposure section of "The
> > Negative."  I could also use this thing for
> > film testing.  I just haven't found a place in
> > the NYC area for the plastic.


From nikon mailing list:
Date: Thu, 30 Aug 2001 
From: John Albino jalbino@jwalbino.com
Subject: Re: expo/disc by George Wallace

Sebastianwrote:
>Maybe can someone tell me how it is with this device... I was at
>http://www.expodisc.com/ but there is no enough information for me.
>Can I use it instead hand light meter, or spot meter?
>What else I can do with it???
>It is very interesting...

What the Expo/Disc does is effectively to turn your camera's built-in
reflected light meter into an incident meter. It does so in the same
essential manner that many hand-held reflected light meters perform
incident readings -- by placing a calibrated semi-translucent "object" over
the meter's sensing cell.

Reflected meters as old and as classic as the early Weston Master series
used to come with a whitish plastic device which fitted over the sensor
cell and then the meter was used as an incident meter.

An "incident meter" is called that because it measures the light falling
onto it from a light source (light "incidence") rather than being reflected
back from a subject.

The Expo/Disc fits onto the front of a camera lens. The camera then is
placed in the subject's position (or similar light) and pointed back,
either at the light source or at the eventual taking position of the photo.
(Whether pointed at the light source or the camera taking position is
mostly a matter of technique and personal calibrations and needs.)

Although the description on the web site is pretty Spartan, it does
describe several uses of the Expo/Disc, perhaps the most exotic of which is
the "flashing" of film in order to increase tonal range. Flashing is a very
old technique not much used any more. It also used to be used to increase
the effective speed of film for old-time "available darkness" shooting.
There are both pre- and post-flashing techniques. Essentially, the film is
exposed to a brief (extremely brief) "flash" of pure light which can either
pre-sensitize the film for additional effective film speed, or increase the
threshold of a film's characteristic curves to spread out the tonal range,
thus allowing for the ability to capture a more contrasty scene than
normally possible. Although lots of experimentation is necessary to achieve
one's personal goals, once established it can be an effective technique. I
personally have not made much use of it, and only used it enough many years
ago to understand the basics of how it worked, but not to become any kind
of "expert" with the technique.

Also described on the Expo/Disc page is probably the simplest use of the
device -- as a "Sunny-16" checker. Any well-calibrated incident meter
should be much more consistent with Sunny-16 than a reflected meter, since
the reflected meter will have many variables introduced into the metering
(including what the meter is pointing at, both color and reflectivity-wise).


As a tool, the Expo/Disc is not that expensive, and certainly could make an
interesting "toy" to play with for a different understanding of exposure
and how one's camera metering system really works. For all practical
purposes Matrix Metering would be useless, and probably prone to wrong
readings, if used with such a device. Spot metering also probably wouldn't
work well. I'd guess the broadest-reading in-camera meter would gain the
best results, although, like most everything photographic, actual
individual testing and calibration techniques would lead to the best 
results.

I've never personally used an Expo/Disc, but (long before I ever heard of
the device) tried to make something similar back in the '60s, and found
that if one spent enough time and effort, such a technique could produce
very good results.
--
John Albino
mailto:jalbino@jwalbino.com


From nikon mailing list:
Date: Thu, 30 Aug 2001 
From: Ron Schwarz rs@clubvb.com
Subject: Re: expo/disc by George Wallace

>I've never personally used an Expo/Disc, but (long before I ever heard of
>the device) tried to make something similar back in the '60s, and found
>that if one spent enough time and effort, such a technique could produce
>very good results.

IIRC Topcon sold something like that, but dome shaped, back in the '60s for
use with their cutting edge TTL SLR.



From nikon mailing list:
Date: Thu, 30 Aug 2001 
From: John Albino jalbino@jwalbino.com
Subject: Re: expo/disc by George Wallace

 Ron Schwarz wrote:

>IIRC Topcon sold something like that, but dome shaped, back in the '60s for
>use with their cutting edge TTL SLR.

I kind of remember that. The Topcon was the very first TTL SLR, and was
really a very strong beast. I think what killed it was that Nikon had a
much more complete system, and ultimately that proved more important than
"who was first."

Also, if I, too, recall correctly, one of the photo magazines at the time
had an article or two on making your own in-camera incident meter by using
half a ping-pong ball on the lens.

Something else I experimented with at the time was making my own 
pseudo-TTK meter by trying to calibrate my Gossen Luna-Pro with taking a 
reading
through the viewfinder of my (plain-prism) Nikon F. This was before Nikon
came out with a TTL prism, which I couldn't have afforded, anyway, since I
already had busted the bankroll getting my F. g> Anyway, the Luna-Pro
certainly was sensitive enough, and indeed I could make it work, but it
wasn't very effective since it wasn't really very feasible for hand-held
readings. The camera pretty much needed to be mounted on a tripod, and it
took some time to take the pseudo-TTL reading, and if I had that much time
available I could just as easily gone right up to the subject and taken a
direct reading. {g}


--
John Albino
mailto:jalbino@jwalbino.com



From nikon mailing list:
Date: Thu, 30 Aug 2001 
From: camdir@aol.com
Subject: Re: Wallace Expo-disc

NikonMF@yahoogroups.com writes:

 Maybe can someone tell me how it is with this device... I was at
 http://www.expodisc.com/ but there is no enough information for me.
 Can I use it instead hand light meter, or spot meter?
 What else I can do with it??? >>

As I recall, it is/was available in various popular filter thread sizes - you
just screwed it to the filter thread and bingo - an incident cone. I think
the supposed advantages of having it on various focal length lenses are
somewhat overstated, though.

Being translucent, it serves virtually no other photographic purpose, however
I do recall an Expo-Discus Olympic trial in the warehouse at Jessops' old HQ.
These little buggers fly about 50' when you get the knack.

Kind regards

Peter


From nikon mailing list:
Date: Thu, 30 Aug 2001 
From: Rich Evans mrklark@yahoo.com
Subject: Re: expo/disc by George Wallace


  by placing a calibrated semi-translucent "object" over the meter's sensing cell
WOW!! Now I know what I can use all those transluscent Nikon body caps for!
;-)

Regards,
Rich



From nikon mailing list:
Date: Thu, 30 Aug 2001 
From: "Stu Turk" sturk@telerama.com
Subject: Re: expo/disc by George Wallace


----- Original Message -----
From: John Albino jalbino@jwalbino.com

> Also, if I, too, recall correctly, one of the photo magazines at the time
> had an article or two on making your own in-camera incident meter by using
> half a ping-pong ball on the lens.

     Wonder if a square of diffused or milk-white plastic slipped into a
filter holder would work?



From nikon mailing list:
Date: Thu, 30 Aug 2001 
From: gwsears@communicomm.com
Subject: Re: expo/disc by George Wallace

I understand a styrafoam cup works about the same when held in
front of the lens.

GeoW



From nikon mailing list:
Date: Thu, 30 Aug 2001 
From: Nikon Cameras NikonCameras@asean-mail.com
Subject: Re: expo/disc by George Wallace

If anyone has access to the filter kits sold by Honeywell for the Strobonar
"potato masher" type of strobes (or can find one set in the back of some photo
store that sold these 1960-70 units), you can take the opal covered egg-shaped
filter and epoxy it to a Nikon snap-on lens shade.  This will give you an
equivalent incident light meter for a Nikon camera.  I used to use this until
the snap-on lens hood fell off and was lost.  It came in a kit of several
filters (red, orange, etc) but you want the opal-colored wide-angle diffuser
one.  I own a Weston Master V with incident cone attachment that is 40 years
old and is still going strong.  You can also get some opal-colored plexiglas at
some do-it-yourself centers or some art-supply centers, cut it to size (52mm,
62mm, 72mm, etc.) and attach this to a filter with the glass removed using
epoxy.


From: twm47099@mthtrains.com (Tom)
Newsgroups: rec.photo.equipment.35mm
Subject: Re: The Expodisc, a grey card alternative?
Date: 3 Jan 2003


Alan Browne alan.browne@videotron.ca wrote 
> Hi Mike,
> The exposdisc
> *might* be amazing but it can't make the scene contrast lower!

Alan,
Actually that is one of the claims for the expodisc.  In Adam's book
"The Negative" he talks about "pre-exposure" or "Pre-flashing" the
negative to reduce scene contrast and capture important shadow detail.
 Essentially, you pre-expose the negative at about -3ev from midtone
on a uniform field.  Then you make a second exposure (but this time of
the actual scene) either at normal or -1 ev.  This doubles the
exposure at zone 2, increasing zone 2 to zone 3.  But at higher zones
the exposures are not increased as much.  For example using a -3ev
preexposure and normal regular exposure you would have the following:

Scene    Modified exposure
Zone         Zone
  0           2.32
  1           2.58
  2           3.00
  3           3.58
  4           4.32
  5           5.17
  6           6.09
  7           7.04

So the 7 ev scene has had its contrast reduced to less than 5, by
bringing up the shadow detail.  Different contrast ranges can be
obtained by using different amounts of pre- and main exposure.

Adams also points out that a uniform light source is required for the
pre-exposure, and that if it was used with coolor film that the color
of the light needs to be neutral (with the scene), unless a color cast
is the objective.  He then goes on to describe a portable light box
that he built.  It is a bit unwieldly for a 35mm shooter.  The
expodisc works very well in this role.  It gives a uniform light
field.  (Some people have told ne that they can see a pattern in the
lighting, but mine don't show this, maybe theirs was an earlier
version??).  It is neutral, so it doesn't add a color cast by itself.
I've use it with my Maxxum 7.  The 7's "Direct Frame Transfer" lets me
take a bracketted set of expodisc pre-exposures and then return the
film to the first frame in the series.  Then I either bracket the main
exposure (usually to make some test exposures) or just use settings
that have worked previously, depending on what I want to do.

Obviously pre-exposure has its limitations (you are in effect fogging
the film) too much and you lose too much contrast.  But it is a tool.

I was surprised at the cost of the exposdics since Mr. Wallace passed
away, I know that mine (72mm dia) didn't cost that much.  I also use
it for incident metering (infrequently and usually more as a learning
exercise).

Tom


From: "Bandicoot" "insert_handle_here"@techemail.com
Newsgroups: rec.photo.equipment.35mm
Subject: Re: The Expodisc, a grey card alternative?
Date: Fri, 3 Jan 2003

...


I read a while back Heather Angel saying that she used a white cap from an
aerosol spray can that just happened to fit perfectly on to one of her
(Nikon) lenses to let her use the TTL meter for incident readings.  She had
tested it and found it produced accurate results.  Don't know how many
others she tested and rejected first though!


Peter


From minolta manual mailing list:
Date: Tue, 9 Dec 2003 
From: xkaes@aol.com
Subject: Re: Re: Questions on Kiron 28-85 f2.8-3.8 Varifocal lens

spud_dude927@yahoo.com writes:
sorry. I meant "I tried the cofee cup thing and I got a different
exposure than when I metered the north sky 45 degrees up at 1 o'clock
*without the cup*. Cofee cup to thick?"


You must use a white styrofoam cup without any printing on it and you must
make sure that your hand doesn't cover any of the cup -- for obvious reasons. 
Still, if you point the styrofoam cup at the sun and then point the camera
without a cup at the northern sky, you are likely to get diffferent readings. The
reflective value of the northern sky can change quite a bit even if there are
no obvious clouds. (I don't know who started the troublesome northern sky
measure.) If you want to test the accuracy of the styrofoam cup -- or the
northern sky for that matter -- just use the f-16 rule. It's printed on the inside
of every Kodak box of film.

Set the lens at f-16 and set the shutter speed at the ISO (ex. 1/125 with ISO
125 film). Your meter should indicate a correct exposure on a sunny mid-day.
It will if you use a syrofoam cup and you point it at the sun. It won't if
you meter most scenes normally -- i.e. without the cup. It won't if you use
an expensive spot meter -- unless you happen to be metering an 18% reflectance
object. It won't if you meter the northern sky -- most of the time. It won't
if the meter is having a "technical difficulty", such as a weak battery. 

Don't like the f-16 rule? Compare the cup to an 18% grey card. It's a cheap
easy way to get MUCH more accurate exposures than you are getting now. 

Joe


From minolta manual mailing list:
Date: Wed, 10 Dec 2003 
From: Fred St. John fstjohn@covad.net
Subject: Re: Re: Questions on Kiron 28-85 f2.8-3.8 Varifocal lens

I read somewhere (but haven't tried it) that half of an egg-shaped
white Leggs pantihose container will also work, and would be a little
more durable.

Fred


From minolta mailing list:
Date: Wed, 10 Dec 2003 
From: xkaes@aol.com
Subject: Re: Re: Questions on Kiron 28-85 f2.8-3.8 Varifocal lens

fstjohn@covad.net writes:
I read somewhere (but haven't tried it) that half of an egg-shaped
white Leggs pantihose container will also work, and would be a little
more durable.

You are correct. Also, there were a few photo products made that consisted
of white plastic disks that screwed onto the front of you cameras. One was the
Wallace EXPO-DISC, and as I recall, Ricoh or Petri or some other camera
manufacturer made one as well. People laugh when I suggest a coffee cup, ut it's
not my idea. It's been around for a long time -- and you'd be surprised how
well it works. Anyone who owned an incident meter can test out the concept as
well. The incident meter and the coffee cup will give the same reading,
because they are really the same thing. An incident meter is just a regular
metering cell with a white disk on top of it. 


From: Simon s.j.harris@ic.ac.uk
Newsgroups: rec.photo.equipment.35mm
Subject: Re: Styrofoam cup metering
Date: Mon, 29 Mar 2004 

Interesting idea Alan, wonder if it would make any improvement if
you could mould the foam over a former to make it into more of a
hemisphere.

An alternative idea might be to try to find a clear plastic dome
of a large enough size and spray paint it with a matt varnish to
give it a diffusing effect. You may have to sample various
Easter eggs/chocolate oranges to find a suitable dome shaped
piece of plastic - ah well - any excuse for more chocolate!!!

Simon.


Alan Browne wrote:
>
> Tried this for curiosity sake with a styrofoam cup...
> ...
> eg: a 1/3 stop difference leading to a slight under exposure, which
> ain't bad for improvised metering. I'll try to get a few more styro
> coffee cups and see what kind of variance/bias there is...
>
> Cheers,
> Alan.


From: Alan Browne alan.browne@FreeLunchvideotron.ca
Newsgroups: rec.photo.equipment.35mm
Subject: Styrofoam cup metering
Date: Mon, 29 Mar 2004


Tried this for curiosity sake with a styrofoam cup...

1. Measured ambient in my living room with a Minolta incident meter:
ISO 800
1 sec
result: f/8


2. At same position as the meter, and pointing the lens the same
direction as the meter had been pointed (with the styrofoam cup over the
lens):
ISO 800
1 sec
result: f/9

eg: a 1/3 stop difference leading to a slight under exposure, which
ain't bad for improvised metering. I'll try to get a few more styro
coffee cups and see what kind of variance/bias there is...

Cheers,
Alan.


From: victorsmind@cox.net (Victorious Mind)
Subject: Re: ExpoDisc
Newsgroups: alt.photography
Date: Tue, 6 Jul 2004 

Hello, Ray Paseur!
You wrote:

> Anybody using one of these filters? What's your experience?
> http://www.expodisc.com/
> Thanks, ~Ray
>
>
I have done alot of research trying to find a less expensive way
of doing the same thing that the expo disc does. This is what I
came up with. Take a white coffee filter and place it over the
lense of your camera. point your camera at the object you want
to photograph, and set your white ballance. This takes care of
the white ballance function of the Expodisc. The issue is the
exposore. This will require a bit of experimentation on your
part. If you layer two or three coffee filters, you will achieve
the 18 percent grey property of the Expodisc. To make the
process of setting my white ballance a bit less goofy looking, I
have laminated two filters. One wallet sized one, and one a bit
larger, that I keep in my camera bag. I use them for practically
every shot where the light changes to reset my white ballance.
The reason why a white piece of paper does not work as well is
because zooming in on an 8x11 sheet will not allow you to take
into concideration, all the colors bouncing around in the entire
shot. By using the Expodisc or my alternative, is that by
placing it on the face of the lense, you can compose your shot
and then set the white ballance so that it accounts for every
color in your shot. If you dont like the results, (but you will)
you have only wasted about a penny on a coffee filter. Let me
know how it turns out.


From: Steve Kramer steve@seatraveler.com
Newsgroups: rec.photo.equipment.35mm
Subject: Re: Expodisc
Date: Wed, 07 Jul 2004 

Karl Winkler wrote:

> Seems though that the whole point of this
> product is for accurately setting the white balance for digital
> cameras. For film cameras, it seems to simply be a method of gaining
> and incident light reading, and is not for any specific film, per se.
> Incident meters for me have worked better in difficult lighting
> situations than ttl meters, but I can't imagine threading this thing
> on and off the camera lens between exposures...

There is no threading used on the Expodisc. It's a press fit that is
very quick and easy. And the disk itself is a Godsend when in tricky
lighting conditions and setting PERFECT white balance and/or exposure.
Since I started using it, I'd hate to be without it. It saves me a lot
of post processing time, is just about unbreakable, and faster and
easier to use than a gray card and actually more accurate!

Steve Kramer
Chiang Mai, Thailand
http://www.photoenvisions.com




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