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.
A 2.35:1 widescreen image letter-boxed in a 1.33:1 screen
A window-boxing image
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).
Widescreen in a control room
Conrad Luperti, J. Marvin Spoor, and William S. Adams with the Natural Vision camera
An early (1994) Sony Widescreen Television