Color Separation Process for Color Printing

The color separation process is used to digitally scan the original and separate it into red, green and blue components. Prior to the development of digital imaging, the traditional method of color separation was to photograph the image three times, each time filtering different light with filters of the corresponding color. After color separation, however, the desired result was three gray images representing the red, green, and blue components of the original:

The next step was to convert each color separation. In generating a negative image of the red component, the resulting image represents the cyan component of the image. Similarly, the negative image of the green component and the blue component are generated so that the magenta and yellow color separations are generated accordingly.

Cyan, magenta, and yellow are subtractive primary colors because each color represents the two additive primary colors remaining after subtracting an additive primary color from white light. Cyan, magenta and yellow are the three main pigments used in color reproduction. Where these three colors are combined in printing to give a reasonable reproduction of the original, this is not the case in practice. Due to the limitations of the ink pigments, the resulting darker colors are dirtier and smudged. To solve this problem, a black plate is also produced to improve the darker colors and increase the contrast of the image. A variety of techniques have been used to create this black plate from the original image; these include gray component replacement, base color removal, and base color addition.