BetterPhoto Q&A
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film rating

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January 24, 2001

When you push a film, you are deliberately underexposing it. You need to do this for the entire roll as the film processing must be modified. When you take it to the lab, you must ask for "push processing" and tell the lab how many stops you pushed the film. Most consumer labs will not know what you are talking about, or if they do, they still cannot process it for you. Usually, only professional labs can perform push processing, and you will pay extra for it compared to normal processing. Your film must be handled and processed separately from other films that were not pushed.

Typically contrast and graininess increases with pushing a film compared to shooting it at its rated speed. With some films, it increases dramatically. Therefore, it is wise to look at all the faster speed ratings for a family of films to see if pushing a slower speed will result in greater granularity than simply using one rated at the higher speed you want. Regardless of what you find regarding grainularity effects, expect increased contrast.

-- John

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January 24, 2001

1. Color negative films:

a. Kodak Supra 400:
A professional film, this can be pushed one stop to EI 800. (You might do better by simply using Supra 800 . . . and shoot this Push 1 _only_ if you don't have any ISO 800 film and need the speed.)

b. Kodak Supra 800:
A professional film, this can be pushed one stop to EI 1600, or two stops to EI 3200.

c. Kodak Royal Gold 1000:
According to the data sheet this can be pulled by up to two stops to EI 250, or pushed by up to one stop to EI 2000. As there is no information about how to modify the C-41 processing for this, your results may vary by doing it. This is a wide latitude film that is forgiving of exposure error.

2. Transparency (slide) films:

a. Kodachrome 200 (KL):
This can be pushed 1-1/3 stops to EI 500, or 2 stops to EI 800.

b. Kodak Ektachrome P1600 (EPH):
A professional film, this is actually an ISO 400 film optimized for Push 2 at EI 1600. It can also be used Push 1 at EI 800. Uses normal E-6 processing for EI 400, E-6P Push 1 for EI 800, and E-6P Push 2 for EI 1600.

NOTE: Any of these films _can_ be pushed to intermediate EI's between those given by Kodak, however the EI's given are the recommended ones for pushing the film. I can only presume that these are EI's for which pushing the film works better. They are also the EI's for which Kodak gives specific instructions in their data sheets for push processing it. Any other EI would require estimating processing times and temperatures by interpolation from the data in their tables.

-- John

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January 25, 2001