Letter-boxing is the practice of transferring film shot in a widescreen aspect ratio to standard-width video formats while preserving the film's original aspect ratio. The resulting video-graphic image has mattes of empty space above and below it; these mattes are part of each frame of the video signal.

Widescreen images are displayed within a set of aspect ratios used in film, television and computer screens. In film, a widescreen film is any film image with a width-to-height aspect ratio greater than 4:3 (1.33:1).