When do you use color subtraction?

Answer 1

Nearly all modern color photographic film processes use subtractive color because it is more efficient. It produces a very good facsimile of the original scene colors with less loss of light than with additive color. Each additive color filter subtracts two-thirds of the white light striking it, while each subtractive color filter transmits two-thirds. With three color dye layers in subtractive color film, all colors can be reproduced: the subtractive primaries are magenta, cyan, and yellow, each of which absorbs its complementary color. Combinations of these three colors can reproduce their shared additive primary. For example, magenta transmits red and blue, while absorbing green light. Cyan transmits blue and green, while absorbing red. When superimposed, both red and green are absorbed and only the shared blue transmission is permitted. By varying the density of each subtractive filter, virtually any color can be reproduced.