Solution of reciprocity law

How to solve the problem of invalidation of reciprocity law of color film?

First of all, you can set the exposure time within the range without worrying about reciprocal failure. For example, if you want to shoot under the exposure conditions of 1/2000 and f/8, you can increase the trigger time of light on the film by changing the exposure index. If the shutter speed is changed to 1/500, the aperture f/ 16, the net exposure is equal, but the time for light to trigger the film is within the safe range.

Second, if you can't do this, it's the second way. Kodak has two kinds of films to avoid the invalidation of reciprocity law: "Wan Li ⅲ professional S-type color film", which is designed for extremely short exposure time. The exposure time can range from110 to110000 seconds. There is no need to add color filters or adjust other exposure conditions. This kind of film, commonly known as "VPS", is packaged in pieces and packages of various main sizes. As mentioned before, VPS is a kind of film that many portrait photographers are happy to use. Because it shows the skin color of the human body very vividly.

"Wanli Ⅱ patent L-type professional color film" is designed for long exposure time-1/50s to 60s. This kind of film has only two packaging sizes: loose-leaf film and 120 film. There is no 35mm specification.

Thirdly, if the above methods are not allowed, we can also adopt compensation methods, that is, adjusting exposure time to compensate for underexposure and adjusting development time to compensate for contrast change. How much should I adjust? Movies are different from movies, and each movie has its own reciprocity law. If you need specific information in this regard, you can consult the manufacturer.

The following table is a general comparison table, which is generally applicable to many black-and-white film. Reciprocal failure compensation original exposure time plus exposure time development time change 1 10000 seconds, half step increase 15% 1/2000 seconds, 1/4 step increase10%/kloc-0.