Aspect ratio Description
1.19:1 "Movietone" - early 35 mm sound film ratio used in the late 1920s and early 1930s, especially in Europe. The optical soundtrack was placed on the side of the 1.33 frame, thus reducing the width of the frame. The Academy Aperture frame (1.37) fixed this by making the frame lines thicker. The best examples of this ratio are Fritz Lang's first sound films: M and The Testament of Dr. Mabuse. This is also roughly identical to the ratio of the physical frame used for anamorphic photography today.
1.25:1 The British 405 line TV system used this aspect ratio from its beginning in the 1930s until 1950 when it changed to the more common 1.33 format.
1.33:1 35 mm original silent film ratio, commonly known in TV and video as 4:3. Also standard ratio for MPEG-2 video compression.
1.37:1 35 mm full-screen sound film image, nearly universal in movies between 1932 and 1953. Officially adopted as the Academy ratio in 1932 by AMPAS. Still occasionally used. Also standard 16 mm.
1.43:1 IMAX format.
1.5:1 The aspect ratio of 35 mm film used for still photography.
1.56:1 Widescreen aspect ratio 14:9. Often used in shooting commercials etc. as a compromise format between 4:3 (12:9) and 16:9, especially when the output will be used in both standard TV and widescreen. When converted to a 16:9 frame, there is slight pillarboxing, while conversion to 4:3 creates slight letterboxing.
1.66:1 35 mm European widescreen standard; native Super 16 mm frame ratio. (5:3, sometimes expressed more accurately as "1.67".)
1.75:1 Early 35 mm widescreen ratio, primarily used by MGM, and since abandoned.
1.78:1 Video widescreen standard (16:9), used in high-definition television, One of three ratios specified for MPEG-2 video compression.
1.85:1 35 mm US and UK widescreen standard for theatrical film. Uses approximately 3 perforations ("perfs") of image space per 4 perf frame; films can be shot in 3-perf to save cost of film stock.
2:1 Original SuperScope ratio, also used in Univisium.
2.2:1 70 mm standard. Originally developed for Todd-AO in the 1950s. 2.21:1 is specified for MPEG-2 but not used.
2.35:1 35 mm anamorphic prior to 1970, used by CinemaScope ("'Scope") and early Panavision. The anamorphic standard has subtly changed so that modern anamorphic productions are actually 2.39,[1] but often referred to as 2.35 anyway, due to old convention. (Note that anamorphic refers to the compression of the image on film to maximize a standard 4 perf academy area but presents the widest of aspect ratios.)
2.39:1 35 mm anamorphic from 1970 onwards. Sometimes rounded up to 2.40.[1] Often commercially branded as Panavision format or 'Scope.
2.55:1 Original aspect ratio of CinemaScope before optical sound was added to the film. This was also the aspect ratio of CinemaScope 55.
2.59:1 Cinerama at full height (three specially captured 35 mm images projected side-by-side into one composite widescreen image).
2.76:1 MGM Camera 65 (65 mm with 1.25x anamorphic squeeze). Used only on a handful of films between 1956 and 1964, such as Ben-Hur (1959).
4:1 Polyvision, three 35 mm 1.33 images projected side by side. Used only on Abel Gance's Napoléon (1927).
Anything filmed in an aspect ratio below the red will result in bars top and bottom.
Edit - You can ignore some as I doubt Abel Gance's Napoléon will be on tv anytime soon.
