in general, a term for how the image appears on the screen based on how it was shot; refers to the ratio of width (horizontal or top) to height (vertical or side) of a film frame, image or screen; the most common or standard aspect ratio in early films to the 1950s was called Academy Aperture (or ratio), at a ratio of 1.33:1 (the same as 4:3 on a TV screen); normal 35mm films are shot at a ratio of 1.85:1; newwidescreen formats and aspect ratios were introduced in the 1950s, from 1.65:1 and higher; CinemaScope (a trade name for a widescreen movie format used in the US from 1953 to 1967) and other anamorphic systems (such as Panavision) have a 2.35:1 AR, while 70mm formats have an AR of 2.2:1;Cinerama had a 2.77:1 aspect ratio; letterboxed videos for widescreen TV's are frequently in 16:9 (or 1.77:1) AR.
— Film Terms