The act of converting an RGB color image into CMYK color image. The act of color separation is a technical function during which critical press specific settings such as GCR, black ink limit and total ink limit are applied to the image. If an image is already CMYK it would be described as being already color separated and would not need to be separated again.
In screen-printing, the pre-press process during which each individual color in the art is isolated for creation of its own stencil. In process-color printing and digital printing, the image is divided into separate stencils for yellow, magenta, cyan, and black. Although the process of making color separations used to be done manually or using colored negatives or filters, today the job is relegated to the computer, which also generates color separations for large-format imaging.