The effect of displaying a wide screen movie on a standard TV set the way it was originally shot in full panoramic format. On the TV, the image frame spans the full width of the screen, but because of the difference in aspect ratios of the two formats (wide screen movie vs. more square TV screen), the vertical height of the frame is reduced. The unused top and bottom areas of the screen appear as black bars.

Major motion pictures are shot with aspect ratios that are even wider than today's 16:9 wide screen TVs. As a result, the letterbox bars may still show, although not as thick as when displayed on a standard 4:3 screen (see aspect ratio for comparison). The term "letterbox" was coined because the wide frame resembles a letter envelope. Contrast with pan & scan. See pillarbox and anamorphic DVD.