Information about Aspect Ratio (image)

The aspect ratio of an image is its displayed width divided by its height (usually expressed as "x:y" or "x×y," with the joining colon or multiplication symbol articulated as the preposition "by" or sometimes "to").

Currently, the most common motion picture film ratios in use are 1.85:1 and 2.39:1^[1]. In video, the two standardized ratios are currently the traditional 4:3 (1.33:1), universal among standard definition video formats, and its modern 16:9 (1.78:1) successor, used in high-definition television and European digital television. Historically, many other aspect ratios no longer in general use have existed in both film and video. Conversion between formats with unequal ratios can be accomplished by either cropping the image to fit the receiving format's ratio or adding black bars (letterboxing or pillarboxing) to retain the original format's ratio. Film ratios tend to be formatted to end with ":1", while video ratios usually prefer to be denoted with whole numbers on both sides of the ratio.

The most common still camera aspect ratios are 4:3 and 3:2, though other ratios such as 5:4, 7:5 and the square format 1:1 are also still found.

The evolution of film and TV aspect ratios

Practical limitations

The size of the image in motion picture formats is dictated by the physical size of the film area between the perforations. The universal standard, as established by William Dickson and Thomas Edison in 1892, is a frame that is four perforations high. The film itself is 35 mm wide (1.38 in), but the area between the perforations is 24.89 mm by 18.67 mm (.980 in by .735 in).^[2] With a space designated for the standard optical soundtrack, and the frame size reduced to maintain a picture that was wider than taller (more mimicking human vision), this resulted in the Academy aperture of 22 mm by 16 mm (.866 in by .630 in) or 1.37:1.

Cinema terminology

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 2.40:1 or just "2.40" (pronounced "two four oh"). The most common projection ratios in American theaters are 1.85:1 and 2.40:1. Some European countries use 1.66:1 as a widescreen standard. 1.33:1 was used for all theatrical films up until the 1950s when 1.85:1 became the standard for US theatrical projection.

Movie camera systems

Development of various camera systems must therefore ultimately cater to the placement of the frame in relation to these lateral constraints of the perforations and the optical soundtrack area. One clever widescreen alternative, VistaVision, used standard 35 mm film running sideways through the camera gate, so that the sprocket holes were above and below frame, resulting in a larger horizontal negative size per frame as the vertical size was now restricted by the perforations. 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 (on standard 4-perforation 35 mm film) to show in the projectors available at theaters. Though the format was briefly revived by Lucasfilm in the 1970s for special effects work that required larger negative size (due to image degradation from the optical printing steps necessary to make multi-layer composites), it went into obsolescence largely due to better cameras, lenses, and film stocks available to standard 4-perforation formats, in addition to increased lab costs of making prints in comparison to more standard vertical processes. (The horizontal process was later adapted to 70 mm film by IMAX.)

Super 16 mm film is frequently used for television production due to its lower cost, lack of need for soundtrack space on the film itself (as it is not projected but rather transferred to video), and aspect ratio similar to 16:9 (Super 16 mm is natively 1.66 whilst 16:9 is 1.78). It also can be blown up to 35 mm for theatrical release and therefore is also used for feature films.

Current video standards

4:3 standard

The 4:3 ratio for standard television has been in use since television's origins and many computer monitors use the same aspect ratio. 4:3 is the aspect ratio defined by the Academy of Motion Picture Arts and Sciences as a standard after the advent of optical sound-on-film. By having TV match this aspect ratio, films previously photographed on film could be satisfactorily viewed on TV in the early days of the medium (i.e. the '40s and the '50s). When cinema attendance dropped, Hollywood created widescreen aspect ratios (such as the 1.85:1 ratio mentioned earlier) in order to differentiate their industry from the TV.

16:9 standard

16:9 (generally named as: "Sixteen-by-Nine") is the international standard format of HDTV as used in Australia, Canada, Japan, South Korea, and the United States, as well as in Europe on HDTV and non-HD widescreen television (EDTV) PALplus. Japan's Hi-Vision originally started with a 5:3 ratio but converted when the international standards group introduced a wider ratio of 5⅓ to 3 (=16:9). The 1.78:1 aspect ratio was the compromise between the 35 mm US and UK widescreen standard (1.85:1) and the 35 mm European widescreen standard (1.66:1) . Many digital video cameras have the capability to record in 16:9. Anamorphic DVD transfers store the information vertically stretched in a 4:3 aspect ratio; if the TV can handle an anamorphic image, it will horizontally decompress the signal to 16:9. If not, the DVD player can reduce scan lines and add letterboxing before sending the image to the TV. Wider ratios such as 1.85:1 and 2.40:1<ref name="anamorphic" /> are accommodated within the 16:9 DVD frame by additional black bars within the image itself. The European Union has instituted the 16:9 Action Plan, just to accelerate the development of the advanced television services in 16:9 aspect ratio, both in PAL and also in HDTV. The Community fund for the 16:9 Action Plan amounted to ECU 228 million.

Visual comparisons

Two aspect ratios compared with images using the same diagonal size.

Previous and presently used aspect ratios

See List of common resolutions for a listing of computer resolutions and aspect ratios.

See List of film formats for a full listing of film formats, including their aspect ratios.

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.
2.00:1	Original SuperScope ratio, also used in Univisium.
2.20:1	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,<ref name="anamorphic" /> 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<ref name="anamorphic" /> 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).

Aspect ratio releases

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 mm film 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 altering the aspect ratio to the television standard of 1.33:1. Because of the varied ways in which films are shot, IAR (Intended Aspect Ratio) is a more appropriate term, but is rarely used.

Modified aspect ratio (MAR)

Modified Aspect Ratio is a home cinema term for the aspect ratio or dimensions in which a film was modified to fit a specific type of screen, as opposed to original aspect ratio. Modified aspect ratios are usually either 1.33:1 (historically), or (with the advent of widescreen television sets) 1.78:1 aspect ratio. 1.33:1 is the modified aspect ratio used historically in VHS format. A modified aspect ratio transfer is achieved by means of pan and scan or open matte, the latter meaning removing the cinematic matte from a 1.85:1 film to open up the full 1.33:1 frame.

Criticism

Multiple aspect ratios create additional burdens on filmmakers and consumers, and confusion among TV broadcasters. It is common for a widescreen film to be presented in an altered format (cropped, letterboxed or expanded beyond the Original Aspect Ratio). It is also not uncommon for windowboxing to occur (when letterbox and pillarbox happen simultaneously). For instance, a 16:9 broadcast could embed a 4:3 commercial within the 16:9 image area. A viewer watching on a standard 4:3 (non-widescreen) television would see an 4:3 image of the commercial with 2 sets of black stripes, vertical and horizontal (windowboxing or the postage stamp effect). A similar scenario may also occur for a widescreen set owner when viewing 16:9 material embedded in a 4:3 frame, and then watching that in 16:9. It is also not uncommon that a 4:3 image is stretched horizontally to fit a 16:9 screen to avoid pillar boxing.

Both PAL and NTSC have provision for some data pulses contained within the video signal used to signal the aspect ratio (See ITU-R BT.1119-1 - Wide-Screen signalling for broadcasting). These pulses are detected by television sets that have widescreen displays and cause the television to automatically switch to 16:9 display mode. When 4:3 material is included (such as the aforementioned commercial), the television switches to a 4:3 display mode to correctly display the material. Where a video signal is transmitted via a European SCART connection, one of the status lines is used to signal 16:9 material as well.

For many artists, however, aspect ratio is determined not by the constraints of the technology or medium, but by the content or the story. Indeed, as long ago as the early 20th century, film directors such as D. W. Griffith, one of the early giants in film, would sometimes change the picture aspect ratio within the film. In "Intolerance", for example, a single shot where a character falls from a high wall has the sides of the vista greatly cropped to enhance the dramatic height of the fall. Today, Directors of Photography are often forced to compose the shot to keep the essential subjects in the "sweet spot" of the frame as a compositional compromise between the intended aspect ratio and the potential future alternate ratios to be presented.

Still photography

Common aspect ratios in still photography include 4:3 (1.33) used by most point-and-shoot digital cameras; 3:2 (1.5) used by 35mm film, APS-C ("classis" mode) and most DSLRs; 1.81:1 (close to 16:9) used by APS-H high definition mode; 3:1 used by APS-P panoramic mode; and 1:1 (square) in a variety of cameras.

Common print sizes in the U.S. (in inches) include 4x6 (1.5), 5x7 (1.4), 4x5 and 8x10 (1.25), and 11x14 (1.27); large-format cameras typical use one of these aspect ratios. Medium-format cameras typically have format designated by nominal sizes in centimeters (6x6, 6x7, 6x9, 6x4.5), but these numbers should not be interpreted as exact in computing aspect ratios.

See also

• Active Format Descriptor (AFD)
• Anamorphic widescreen
• Four Thirds System
• Full frame
• Letterbox
• List of common resolutions
• List of film formats
• Motion picture terminology
• Pan and scan
• Paper size
• Television & aspect ratio
• Widescreen
• Widescreen display modes

References

Cited references

General references

External links

• The Letterbox and Widescreen Advocacy Page
• American Widescreen Museum
• Widescreen Apertures and Aspect Ratios
• Aspect - combined aspect ratio, frame size and bitrate calculator
• Calculator to Determine Size of 4:3 Image on 16:9 Screen (middle of the page)
• Aspect Ratios Explained: Part 1 Part 2
• Aspect Ratios: Digital Cameras, Print and Sensor Sizes
• Explanation of TV Aspect Ratio format description codes
• Number of DVDs for each aspect ratio
• TECHNICAL BULLETIN Understanding Aspect RatiosPDF (708 KiB)
• SCADplus: 16:9 Action plan for the television in the 16:9 screen format - European Union