Organization: University of Illinois at Chicago
Date: Thursday, 17 Dec 1992 01:01:19 CST
From: Rich Chong <U41602@uicvm.uic.edu>
Newsgroups: rec.photo
Subject: Re: color change w/exposure change: Why?
 <BzD4n8.6pu@javelin.sim.es.com>

>In article <1992Dec10.155126.1@pearl.tufts.edu> rsmith@pearl.tufts.edu writes:
>>I've got a question about some photos I recently took.  It was a foggy night
>>in Cambridge, and I went out to take some long-exposure shots in the fog.
>>I used Eastman 5296 (this is an ISO 400 color print film, process ECN-2),
>>fairly wide aperature (f 3.5 or 4) and exposures bracketed from 1/2 sec to
>>16 seconds (on a tripod, of course).  I got the prints back and, as expected,
>>the shorter exposures are underexposed, with a greenish-yellow sickly cast
>>to the light.  The longer exposures are brighter, of course, but now the light
>>(and especially the sky) has a reddish-orange cast to it.  Why should a change
>>in exposure alter the color balance like that?  I'm not too good at judging
>>color from the negatives, so I can't even be sure it's the film; it could
>>be the print-making.  Any ideas out there?
>>
>The color differences in your prints are most certainly the result of the
>way the prints were made.  Just for information, Eastman 5296 is a tungsten-
I disagree, the basic problem is reciprocity failure (as others have noted).
Kodak optimized that film for cinematography work. i.e. exposures much much
faster than 16 seconds! Since it wasn't made for consumer use, it also isn't
built with the exposure lattitude of normal consumer film.

>balanced motion picture film, rated EI 500 with Tungsten (3200 K) lights,
>or rated EI 320 with a #85 filter.  I would presume that the lighting in
>your picture was a mix of tungsten, mercury vapor, sodium vapor, fluorescent
>and who-knows-what.  Given that mix of film and lighting, it is hard to say
>what a "correct" color balance is.  I would also presume that you got your
If a correct balance is even obtainable! (probably not)

>film and processing are from one of the MP-film labs (Seattle FW, RGP, Dale,
>Signature, etc).  If so, communicating with them and getting prints redone by
>long distance is frustrating.  These type films require a different
>enlarger color balance than the typical consumer films, and so a local lab
>will probably have a difficult time with them.
I've experienced a wide flux in color balancing even typical consumer film.
For me, I can get decent 1st time color balance if I use the same filtration
for film of the same exact brand, speed, lighting, and enlarger exposure time.
Modify any of those variables, and I had to rebalance the color from scratch.
Of course, I havn't done extensive tests, but it is what I experienced. I'm
sure that even a batch change of film, paper, and chemistry will cause changes.
So what i'm basiclly saying is that local labs wont have a balancing problem
*because* of the strange film you used, but of the rough time of balancing any
reciprocity problem negative. To stress what someone already said, the big
prob is that the different color layers in the film have different degrees
of reciprocity. (e.g. Normal Kodacolor Gold 100 film: To get the same color
balance on the film, of a properly exposed 1/10sec exposure, in a 1sec exposure
(i.e. linearly what your camera thinks should be a 1sec exposure), Kodak
recomends that you really make it a 2 second exposure and add a CC20Y filter!
CC20Y is a deep yellow filter. Of course, the normal consumer won't do this
and has unknowingly learned to deal with colors which aren't quite right.
The lab helps out by automatically compensating for the underexposure and
perhaps taking out some yellow in the print filtration, but that throws other
colors off a bit. Kodak doesn't even recommend that you use their consumer
Kodacolor Gold 100 at 10 seconds or greater (if you really care about color).

>My suggesting would be to find a friend with a color darkroom.  Plan on
>spending an evening and play with the color balance until you get what you
>want.  If you can find a cooperative local lab that will work with you, you
>may be able to get good prints that way.
Go ahead, but don't hold your breath for excellent prints. Balancing for a
grey spot in the negative will probably put the fleshtones or sky outta whack.
I've only had two fun attempts at correcting bad negatives. In the worst case,
I decided to balance for fleshtones, but the sky wasn't grey-blue, it was deep
orange. Freeky looking, but neat. I played with burning the sky out (darker),
and even tried to mask and reexpose to correct the freekiness, but finally
decided to stop playing around($) and just enlarge and crop the sky out.

>
>PS:  I'm not trying to denigrate the motion-picture films.  I've used them
>successfully in certain applications.  However, you will have more success
>if you do the entire job yourself:  film processing and printing.  Otherwise,
>you would be better to stay with the C-41 films.
>
>Ron Speirs, Evans & Sutherland Computer Corp., Salt Lake City, Utah
>

Sorry for all the detail. Just neat stuff to talk about!


Rich Chong,  RC Tech Enterprises, Inc.