The aspect ratio is the ratio of width to height of an image, display or film. The aspect ratio is calculated from the ratio of the horizontally and vertically displayed pixels of an image.
The standardized aspect ratio for classic televisions was 4:3 or 1.33:1. Later, the 16:9 format became standard for televisions and displays. This format is also known as widescreen. Motion pictures with a 21:9 (2.35:1) aspect ratio are referred to as cinema widescreen, panavision, or cinemascope. The historical cinema format has an aspect ratio of 17:9, and this format continues to be used in digital cinema technology in D-Cinema.
In addition to these standardized television and cinema formats, there are various other widescreen formats in computer technology with aspect ratios of 5:4, 15:9, 18:10 and 16:10.
DVDs store video in 4:3 or 16:9 television formats. In addition, DVDs can store movies in letterbox, pan-and-scan, and anamorphic widescreen.