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Rating Film Speed Based on tests with my lab, I rate my film the way I think it comes out the best. So, my process goes something like this, I'll take a roll of test shots with ISO 400 film and write down each exposure. Then when I get the negatives and prints back, I look at the prints, and see which ones have the best color, for color (no science here). Whatever looks best on the print and negative, I use that as my basis for my film rating. It's not technical at all, but it works because I use what "looks" best to me, therefore, to my clients, as well. I do the same for black and white, although, I am not as particular about black and white, except for the negative. the print I don't care so much because black and white prints can be virtually totally manipulated as long as you have a good negative. But, back to color... So, what I do is expose 400 speed film at the same exposure, but I keep chaging the ISO every few frames, and I write down exactly what I am doing. So, when I have the film processed, it is processed as 400 speed film. What would happen, if I rate my 400 speed film at 250, if I tell the lab to process it at 250. I'm sure it would change things, but I just wanted to see what y'all had to add. Other than saying, just test it out for yourself, is this adding to many variables, or is it a worthwhile experiment. Does anyone out there shoot at the film speed (so, shoot 400 using 400 ISo setting on your gear), but then have it pushed or pulled a little? Is there an advantage to doing that? Just wondering... Jerry
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- Gregory LaGrange Contact Gregory LaGrange Gregory LaGrange's Gallery |
would lower contrast. might get you the high key, dreamy, pastel watercolor look.
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Jon Close |
Exposing and developing ISO 400 film at 250 is a +2/3 stop "pull." However, C-41 print film does not push/pull develop the same way one does traditional black & white or slide film. Where normal development times for black & white films variy by ISO and even film brand, all C-41 films (whether ISO 100, 200, 400, 800, 1600) are developed for the same amount of time. "Push" processing C-41 generally is done by increasing the time in the 1st developer by 30 sec./stop (100°F), but is not recommended by any manufacturers (notable exception being Kodak's 400UC and Portra 800) due to inconsistent color shifts. None recommend "pulling" C-41 film. On top of that, C-41 print film has very wide exposure latitude, as much as -2 to +3 stops. It is much less sensitive to changes in exposure rating and development than slide or b&w. I would not expect much noticable effect from rating 400 film at 250 and developing normally other than slightly greater contrast and color saturation. I could be wrong, but I don't think shortening the development time to compensate for shooting at 250 would be beneficial.
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Thanks for the info Jon. I know very little about processing in C-41, but I used to do my own BW development. So, I do know a bit about that. What I'm doing now works well for me, so I'll keep doing it, I was just wondering. Thanks for the info. Jerry
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