Aspect ratio image: Encyclopedia - Aspect ratio image

Aspect ratio (image)

The aspect ratio of an image is its displayed width divided by its height (usually expressed as "x:y"). For instance, the aspect ratio of a traditional television screen is 4:3, or 1.33:1. High definition television uses an aspect of 16:9, or about 1.78:1. Aspect ratios of 2.39:1 (2.35:1 prior to SMPTE revision in 1970) or 1.85:1 are frequently used in cinematography, while the aspect ratio of a sync-sound 35 mm film frame is around 1.37:1 (also known as "Academy" ratio). Silent films which used the full frame were shot in 1.33:1.

Aspect ratio image - The evolution of film and TV aspect ratios

The 4:3 ratio for standard television has been in use since television's origins and many computer monitors use the same aspect ratio. Since 4:3 is the aspect ratio of the usable frame within the Academy format once the soundtrack had been taken into account, films could be satisfactorily viewed on TV in the early days of the medium. When cinema attendance dropped, Hollywood created widescreen aspect ratios to immerse the viewer in a more realistic experience and, possibly, to make broadcast films less enjoyable if watched on a regular TV set.

16:9 is the format of Japanese and American HDTV as well as European non-HD widescreen television (EDTV). Many digital video cameras have the capability to record in 16:9. Anamorphic DVD transfers store the information in 16:9 vertically stretched to 4:3; if the TV can handle an anamorphic image the signal will be de-anamorphosed by the TV to 16:9. If not, the DVD player will unstretch the image and add letterboxing before sending the image to the TV. Wider ratios such as 1.85:1 and 2.39:1 are accommodated within the 16:9 DVD frame by adding some additional masking within the image itself.

Within the motion picture industry, the convention is to assign a value of 1 to the image height, so that, for example, an anamorphic frame is described as 2.39:1 or just "2.39". This way of speaking comes about because the width of a film image is restricted by the presence of sprocket holes and a standard intermittent movement interval of 4 perforations, as well as an optical soundtrack running down the projection print between the image and the perforations on one side. The most common projection ratios in American theaters are 1.85 and 2.39.

Development of various camera systems must therefore ultimately cater to the placement of the frame in relation to these lateral constraints. For example, one clever widescreen process, VistaVision, used standard 35mm film running sideways through camera gate, so that the sprocket holes were above and below frame, resulting in a larger negative size per frame. However, the 1.5 ratio of the initial VistaVision image needed to be cropped down to 1.85 and optically converted to a vertical print for projection. Though the format was briefly revived by Lucasfilm in the 1970s for special effects work that required larger negative size due to image degradation, it went into obsolescence largely due to better cameras, lenses, and film stocks, in addition to increased lab costs of making prints in comparision to more standard vertical processes. (The horizontal process was later adapted to 70mm film by IMAX.)

The 16:9 format adopted for HDTV is actually narrower than commonly-used cinematic widescreen formats. Anamorphic widescreen (2.39:1) and American theatrical standard (1.85:1) have wider aspect ratios, while the European theatrical standard (1.66:1) is just slightly less. (IMAX, contrary to some popular perception, is 1.33:1, the traditional television aspect ratio.)

Super 16mm film is frequently used for television production due to its lower cost, lack of need for soundtrack space on the film itself, and aspect ratio similar to 16:9 (Super 16mm is natively 1.66 whilst 16:9 is 1.78).

The term is also used in the context of computer graphics to describe the shape of an individual pixel in a digitized image. Most digital imaging systems use square pixels—that is, they sample an image at the same resolution horizontally and vertically. But there are some devices that do not (most notably various digital television formats) so a digital image scanned at twice the horizontal resolution to its vertical resolution might be described as being sampled at a 2:1 aspect ratio, regardless of the size or shape of the image as a whole.

Aspect ratio image - Historic and commonly used aspect ratios

• 1.19: "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 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
• 1.25: Commonly used computer resolution of 1280x1024. Native aspect ratio of many LCDs.
• 1.29: Ratio of US Letter size paper (11:8.5 inches), in landscape format.
• 1.33: 35 mm original silent film ratio, common in TV and video as 4:3. Also standard ratio for IMAX.
• 1.37: 35 mm full-screen sound film image, nearly universal in movies between 1928 and 1953. Officially adopted as the Academy ratio in 1932. Still occasionally used. Also standard 16 mm.
• 1.414: Aspect ratio of standard ISO paper sizes (A4, A3, et cetera). Also the square-root of 2.
• 1.5: Wide-aspect computer display (3:2). Used in Apple Powerbook G4 15.2" displays with resolutions of most recently 1440x960. The native aspect ratio of 4x6 film photos. Also the native NTSC DVD-Video resolution, 720x480, although most videos use non-square pixels for a 4:3 ratio.
• 1.6: computer display widescreen (8:5, commonly referred to as 16:10). Used in WSXGAPlus, WUXGA and other display resolutions.
• 1.66: 35 mm European widescreen standard, also Super 16 mm.
• 1.75: early 35 mm widescreen ratio, since abandoned.
• 1.78: video widescreen standard (16:9). Also used in US high-definition television.
• 1.85: 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.
• 2.20: 70 mm standard. Originally developed for Todd-AO in the 1950s.
• 2.35 : 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, but often referred to as 2.35 anyway, due to old convention. No recent anamorphic films are 2.35. However, there is a re-emerging trend to shoot 2.35 using spherical lenses by hard-matting the film gate to 2.35. This recent re-emergence has been catalysed by the digital intermediate process.
• 2.39: 35 mm anamorphic from 1970 onwards. Sometimes rounded up as 2.4. Sometimes refered to as 'Scope.
• 2.59: Cinerama at full height (three specially captured 35 mm images projected side-by-side into one composite widescreen image).
• 2.76: 70 mm anamorphic (Ultra Panavision). Only used on a handful of films between 1956 and 1964, such as Ben-Hur (1959).
• 4.00: Polyvision, three 35 mm 1.33 images projected side by side. Only used on Abel Gance's Napoléon (1927).

Aspect ratio image - Original aspect ratio OAR

Original Aspect Ratio (OAR) is a home cinema term for the aspect ratio or dimensions in which a film or visual production was produced—as envisioned by the people involved in the creation of the work. As an example, the film Gladiator was released to theaters in the 2.39:1 aspect ratio. It was filmed in Super 35 and, in addition to being presented in cinemas and television in the original aspect ratio of 2.39:1, it was also broadcast without the matte its original aspect ratio release had.

Aspect ratio image - Criticism

Multiple aspect ratios create additional burdens on consumers and confusion among TV broadcasters. It is not uncommon for a widescreen program to embed a 4:3 commercial. A person owning a 4:3 set would see an image with 2 sets of black stripes, vertical and horizontal (matchboxing). A similar scenario may also occur for a widescreen set owner when viewing 16:9 material embedded in a 4:3 frame. It is also not uncommon that the image is stretched horizontally or vertically. These artifacts can't be dismissed as negligence on the part of program vendors. They could be avoided if the decision about widescreen format standards were taken more seriously. There is good reason for TV screen design to abandon artifacts of the analog era, and start to mimic computer monitors.

See also

• motion picture terminology
• letterbox
• widescreen
• pan and scan
• television
• list of fax terms
• paper size

Adapted from the Wikipedia article "Aspect ratio image", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki