Color printing is based on subtractive color mixing. The printed image is created by printing several individual colors whose printing dots lie close together and are no longer visible to the eye as individual dots.
In subtractive color mixing, the largest possible color space is achieved by using the three colors cyan (C), magenta (M) and yellow (Y). Since the individual spectral colors have deviations from the theoretical values, the CMY color model is supplemented by depth information (K) for better contour and contrast representation, which is an additional black print. This results in the CMYK color model.
In order to create a color print, the individual color components for the CMY colors and for black (K) must be calculated from the color mixture or from another color model. This color separation is called color separation. The color separation program delivers the three color separations for CMY and a fourth for depth. These four files are needed in color printers or imagesetters for printing or film exposure.