Separating a picture by colors in order to make negatives and plates for color printing. The four-color process requires four separations: cyan, magenta, yellow and black (CMYK). See OPI and DCS.
The separations are printed individually in this picture to show how each of the four inks contributes to the total image. Typically, separations are put on film, and the printing plates are made from the film. (Image courtesy of Intergraph Computer Systems.)