colour separation

Process of splitting a full-colour image into separate colour layers to allow professional printing. Typically the minimum number of colours is three (cyan, magenta, and yellow) plus black.

Graphics software is used to analyse the image and produce four different colour pictures that will recreate the original image when overlaid. This process is used by magazines and newspapers - control colour blocks printed on the page (usually near the fold or spine) show how many colours are used, since simple three-colour separation is often not sufficient for true photographic reproduction.