How to solve the problem of the invalidation of the reciprocity law of color film?
first, you can set the exposure time within the range without worrying about reciprocal failure. For example, if you want to shoot under exposure conditions of 1/2 and f/8, you can change the exposure index to increase the trigger time of light on the film. If the shutter speed is changed to 1/5 and the aperture is f/16, the net exposure is equal, but the time when light triggers the film is within the safe range.
second, if you can't do this, it's still the second way. Kodak has two kinds of films to avoid the failure of reciprocity law: "Wanli ⅲ professional S-type color film", which is designed for extremely short exposure time. The exposure time can be from 1/1 to 1/1 seconds. There is no need to add color filters or other adjustment of exposure conditions. This kind of film is commonly called "VPS", and it is packaged in various main sizes of loose sheets and rolls. It has been mentioned that VPS is a kind of film that many portrait photographers are happy to use. Because it expresses the skin color of the human body very brightly.
"Wanli Ⅱ patent L-type professional color film" is designed for extremely long exposure time-1/5 seconds to 6 seconds. This film only has two kinds of packaging sizes: loose leaf film and 12 film. There is no 35mm specification.
third, if the above methods are not allowed, we can also take compensation methods, that is, adjust the exposure time to compensate for insufficient exposure and adjust the development time to compensate for contrast variation. How much should I adjust? Film and film are different, and each film has its own reciprocity law. If you need this specific information, you can consult the manufacturer.
The following table is a general comparison table, which is generally applicable to many black and white films. Reciprocity failure compensation Original exposure time plus exposure time development time changes by 1/1 seconds, half step increases by 15%, 1/2 seconds increases by 1/4 step increases by 1%, 1/1 seconds increases by one step (i.e. total 2 seconds) decreases by 1%, 1 seconds increases by 2 steps (i.e. total 5 seconds) decreases by 2%, 1 seconds increases by 3 steps (i.e. total 8 seconds)