Keying is the process of isolating a foreground subject against a background area of uniform color or brightness to generate an alpha channel (a matte) based on the shape of the colored area. Keying is commonly performed on subjects photographed against a blue- or green-colored background, but keys can be based on any color (color keying), or on a specific range of brightness values (luma keying).

The keying filters in Motion offer a powerful and comprehensive set of tools for creating expert color and luma keys. Best of all, the Motion keying filters are easy to use.

Figure. A greenscreen clip, and the same clip keyed over a background.