Trapping

Trapping is the process of creating slight overlaps between abutting colored objects within a document. It compensates registration errors between printing plates and printing towers to avoid potential gaps between colors in the design.

In general, light colored objects spread or expand into dark colored objects, as this is less noticeable for the eye than changes in light objects. The opposite can also happen: darker colored objects shrink into light colored object. This is called a choke and generally applied when the darker colored object is on top of the light one.

A color is defined darker or lighter than another color depending on the luminance or Lab value.