Academy ratio
The Academy ratio of 1.375:1 (abbreviated as 1.37:1) is an aspect ratio of a frame of 35 mm film when used with 4-perf pulldown.[1][2] It was standardized by the Academy of Motion Picture Arts and Sciences as the standard film aspect ratio in 1932, although similar-sized ratios were used as early as 1928.[1][2]
Technical details[edit]
The Academy ratio is not created in the camera, which has continued to use the full frame silent aperture gate for all 4-perf spherical filming.[1][2] Rather, it is created in the married print, when the optical soundtrack and frame lines are added. Though most non-anamorphic film prints with a soundtrack are now framed to one of the non-anamorphic widescreen ratios, from 1.6 to 1.85, some still retain Academy-sized frames.[1][2] These frames are then cropped in the projector by means of aperture masks used in the projector's gate in conjunction with a wider lens than would be used for projecting Academy ratio films.[1][2]
During filming, using the 4-perf frame for widescreen framing when spherical lenses are used is sometimes considered to be wasteful in terms of the cost of film stock and processing, especially in the case of television, which does not require a film print. The 3-perf pulldown process was originally proposed in 1973, developed by Miklos Lente in 1976, and further developed by Rune Ericson in 1986 to solve this problem.[9]