Subtractive color process

SUBTRACTIVE COLOR PROCESS. A method of photographic color synthesis using two or more superimposed colorants, which selectively absorb their complementary colors from white light. 

Copper phthalocyanine blue pigments have been widely used in the subtractive color process, e.g., in offset printing inks. The three primary colors of this process are cyan, yellow and magenta. Beta-form phthalocyanine blue is the pigment of choice for the cyan colorant. 

In this application, the process analyzer is used in the vis-NIR spectral region to measure the clear top layer on a co-extruded polymer film. The bottom layer is pigmented to an opaque white color and its thickness cannot be determined by this method. Prior to the installation of the fiber-optic spectroscopy system, film samples were measured manually in the laboratory by a subtractive scheme. First, the total thickness of a sample was measured on a manual profilometer. The top layer of the polymer was removed with methylene chloride. The sample was then repositioned on the profilometer as closely as possible to the originally measured spot and the thickness of the second white layer was determined. The thickness of the top layer was then determined by difference. 

Given the maximum deviation between local space average color and the pixel intensity, the output pixels are calculated as follows. First, local space average color is subtracted from the current intensity. Then, the deviation dj is used to rescale the difference. Henceforth, we drop the coordinate of the current processing element. 

In terms of color, we have additive processes (emittance) and subtractive processes (reflectance). If we wish to match colors, the primary colors are quite different, namely-... 

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