structural:scholar_edition, quality:corruption
Aspect ratio and framing

The aspect ratio of an image is the ratio of its width to its height. This can be expressed either as a ratio of 2 integers, such as 4:3, or in a decimal format, such as 1.33:1 or simply 1.33. Different ratios provide different aesthetic effects. Standards for aspect ratio have varied significantly over time.

During the silent era, aspect ratios varied widely, from square 1:1, all the way up to the extreme widescreen 4:1 Polyvision. However, from the 1910s, silent motion pictures generally settled on the ratio of 4:3 (1.33). The introduction of sound-on-film briefly narrowed the aspect ratio, to allow room for a sound stripe. In 1932, a new standard was introduced, the Academy ratio of 1.37, by means of thickening the frame line.

For years, mainstream cinematographers were limited to using the Academy ratio, but in the 1950s, thanks to the popularity of Cinerama, widescreen ratios were introduced in an effort to pull audiences back into the theater and away from their home television sets. These new widescreen formats provided cinematographers a wider frame within which to compose their images.

Many different proprietary photographic systems were invented and used in the 1950s to create widescreen movies, but one dominated film: the anamorphic process, which optically squeezes the image to photograph twice the horizontal area to the same size vertical as standard "spherical" lenses. The first commonly used anamorphic format was CinemaScope, which used a 2.35 aspect ratio, although it was originally 2.55. CinemaScope was used from 1953 to 1967, but due to technical flaws in the design and its ownership by Fox, several third-party companies, led by Panavision 's technical improvements in the 1950s, dominated the anamorphic cine lens market. Changes to SMPTE projection standards altered the projected ratio from 2.35 to 2.39 in 1970, although this did not change anything regarding the photographic anamorphic standards; all changes in respect to the aspect ratio of anamorphic 35 mm photography are specific to camera or projector gate sizes, not the optical system. After the "widescreen wars" of the 1950s, the motion-picture industry settled into 1.85 as a standard for theatrical projection in the United States and the United Kingdom. This is a cropped version of 1.37. Europe and Asia opted for 1.66 at first, although 1.85 has largely permeated these markets in recent decades. Certain "epic" or adventure movies utilized the anamorphic 2.39 (often incorrectly denoted '2.40')

In the 1990s, with the advent of high-definition video, television engineers created the 1.78 (16:9) ratio as a mathematical compromise between the theatrical standard of 1.85 and television's 1.33, as it was not practical to produce a traditional CRT television tube with a width of 1.85. Until that change, nothing had ever been originated in 1.78. Today, this is a standard for high-definition video and for widescreen television.