The visual effect of black bars on the top and bottom of the screen when a movie with a wide aspect ratio is displayed on a TV that is not as wide. The black bars compensate for the reduced vertical height of the movie frames. This was a common experience on earlier TV sets if the movie was not reformatted for TV viewing (see pan & scan). The term "letterbox" was coined because the wide frame resembles the size of a letter envelope. See pillarbox, aspect ratio and anamorphic DVD.
Standard vs. Wide Screen TVWhen a wide screen movie played on an earlier TV (left), the image was reduced vertically, producing the letterbox effect. (Image courtesy of Intergraph Computer Systems.)
Still Present on Modern TVsMany major motion pictures are shot in full panoramic format with aspect ratios that are still much wider than today's 16:9 wide screen TVs. As a result, the letterbox black bars are still common.
