The aspect ratio of an image is its width divided by its height. An image (from Latin imago) or picture is an artifact usually two-dimensional that has a similar appearance to some subject &mdashusually
Aspect ratios are mathematically expressed as x:y (pronounced "x-to-y") and x×y (pronounced "x-by-y"). The most common aspect ratios used today in the presentation of films in movie theaters are 1. 85:1 and 2. 39:1[1]. Two common videographic aspect ratios are 4:3 (1. Videography refers to the process of capturing moving Images on Electronic media (e 33:1), universal for standard-definition video formats, and 16:9 (1. 78:1), universal to high-definition television and European digital television. High-definition television (HDTV is a Digital television Broadcasting system with higher resolution than traditional television systems (standard-definition Digital television (DTV is the sending and receiving of moving images and sound by discrete ( digital) signals in contrast to the analog signals used by Other cinema and video aspect ratios exist, but are used infrequently. In still camera photography, the most common aspect ratios are 4:3 and 3:2, though other aspect ratios, such as 5:4, 7:5, and 1:1 (square format), are used. A Still camera is a type of Camera used to take Photographs Traditional cameras capture light onto Photographic film.
Converting formats of unequal ratios is done by either cropping the original image to the receiving format's aspect ratio, or by adding horizontal mattes (letterboxing) or vertical mattes (pillarboxing) to retain the original format's aspect ratio. Letterboxing is the practice of transferring Widescreen Film to Video formats while preserving the film's original aspect ratio. The pillar box effect occurs in Widescreen video displays when black bars ( Mattes or masking are placed on the sides of the image Cinematographic aspect ratios are usually denoted as a decimal fraction width to unit height, while videographic aspect ratios are usually denoted by ratios of whole numbers.
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In motion picture formats, the physical size of the film area between the sprocket perforations determines the image's size. The universal standard (established by William Dickson and Thomas Edison in 1892) is a frame that is four perforations high. William Kennedy Laurie Dickson (3 August 1860 &ndash 28 September 1935 was an Anglo - Scottish Inventor who devised an early motion picture The film itself is 35 mm wide (1. 38 in), but the area between the perforations is 24. 89 mm×18. 67 mm (0. 980 in×0. 735 in). [2] With a space designated for the standard optical soundtrack, and the frame size reduced to maintain an image that is wider than taller (mimicking human eyesight), this resulted in the Academy aperture of 22 mm×16 mm (0. Sound-on-film refers to a class of Sound film processes where the sound accompanying picture is physically recorded onto photographic film usually but not always the same 866 in×0. 630 in) or 1. 37:1 aspect ratio.
The motion picture industry convention assigns a value of 1. 0 to the image’s height, thus, an anamorphic frame is described as 2. Anamorphic format is a term that can be used either for the Cinematography technique of capturing a Widescreen picture on standard 35 mm film, or other 40:1 or 2. 40 ("two-four-oh"). In American cinemas, the common projection ratios are 1. 85:1 and 2. 40:1. Some European countries have 1. 66:1 as the widescreen standard. 1. 33:1 was used for all cinema films until the 1950s. By a 'strange coincidence,' 1. 33:1 is the screen ratio of 'standard' television broadcasts. When television became a threat to movie audiences, Hollywood gave birth to a large number of wide-screen formats: Cinemascope, Todd-AO, and VistaVision (to name just a few). During the 1950s the 1. 85:1 aspect ratio became one of the most common cinema projection standards in the U. S. .
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. VistaVision is a variant of the 35 mm motion picture film format created by Paramount Pictures in 1954 based on the Glamorama and Superama 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. 35 mm film is the basic Film gauge most commonly used for both still Photography and Motion pictures, and remains relatively unchanged since its 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. Lucasfilm Limited' is an American Film production company founded by George Lucas in 1971, based in San Francisco California This article is about the Decade 1970-1979 For the Year 1970 see 1970. (The horizontal process was later adapted to 70 mm film by IMAX. IMAX (short for Image MAXimum is a Film format created by Canada 's IMAX Corporation that has the capacity to display images of far greater size and )
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.
The 4:3 ratio (generally named as: "Four-Three", "Four-by-Three" or "Four-to-Three") for standard television has been in use since television's origins and many computer monitors use the same aspect ratio. A visual display unit, often called simply a monitor or display, is a piece of Electrical equipment which displays images generated from the Video 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. The Academy of Motion Picture Arts and Sciences ( AMPAS) is a professional honorary organization ostensibly dedicated to the advancement of the arts and sciences of Motion Sound-on-film refers to a class of Sound film processes where the sound accompanying picture is physically recorded onto photographic film usually but not always the same 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 1940s and the 1950s). When cinema attendance dropped, Hollywood created widescreen aspect ratios (such as the 1. Cinemaaustraliajpg|thumb|A movie theater in Australia ]]A movie theater, movie theatre, picture theatre or cinema is a venue A widescreen image is a film computer or television image with a wider and shorter aspect ratio than the standard Academy frame developed during the Classical 85:1 ratio mentioned earlier) in order to differentiate their industry from the TV.
16:9 (generally named as: "Sixteen-Nine", "Sixteen-by-Nine" or "Sixteen-to-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. High-definition television (HDTV is a Digital television Broadcasting system with higher resolution than traditional television systems (standard-definition For a topic outline on this subject see List of basic Australia topics. Country to "Dominion of Canada" or "Canadian Federation" or anything else please read the Talk Page For a topic outline on this subject see List of basic Japan topics. South Korea, officially the Republic of Korea and often referred to as Korea ( Korean: 대한민국 tɛː The United States of America —commonly referred to as the High-definition television (HDTV is a Digital television Broadcasting system with higher resolution than traditional television systems (standard-definition Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic Enhanced-definition television, extended-definition television, or EDTV is a CEA marketing shorthand term for certain Digital television PALplus is an extension of the PAL analogue broadcasting system for transmitting programs without sacrificing vertical resolution 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), invented by Kerns H. MUSE ( Multiple Sub-nyquist Sampling Encoding System also known as Hi-Vision for marketing purposes was an early high-definition analog television standard developed Powers in 1984. Year 1984 ( MCMLXXXIV) was a Leap year starting on Sunday (link displays the 1984 Gregorian calendar) 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. Digital video is a type of Video recording system that works by using a Digital rather than an analog video signal Anamorphic DVD transfers store the information vertically stretched in a 3:2 aspect ratio; if the TV can handle an anamorphic image, it will horizontally decompress the signal to 16:9. Anamorphic widescreen is a videographic technique utilising rectangular (wide pixels to store a Widescreen image to standard 43 aspect ratio. DVD (also known as " Digital Versatile Disc " or " Digital Video Disc " - see Etymology)is If not, the DVD player can reduce scan lines and add letterboxing before sending the image to the TV. Letterboxing is the practice of transferring Widescreen Film to Video formats while preserving the film's original aspect ratio. Wider ratios such as 1. 85:1 and 2. 40:1[1] are accommodated within the 16:9 DVD frame by additional black bars within the image itself. The European Union and Federation of Bosnia and Herzegovina have 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 European Union ( EU) is a political and economic union of twenty-seven member states, located primarily in The Federation of Bosnia and Herzegovina ( Federacija Bosne i Hercegovine Федерација Босне и Херцеговине) is one of the two political PAL, short for Phase Alternating Line, is a colour -encoding system used in Broadcast television systems in large parts of the world High-definition television (HDTV is a Digital television Broadcasting system with higher resolution than traditional television systems (standard-definition The Community fund for the 16:9 Action Plan amounted to €228 million. Please update other articles as well to avoid contradiction within Wikipedia e
In Europe 16:9 is used in the U.K. (Almost all Mainchannels are in 16:9), France (TF1, France Télévisions, NRJ 12), Germany (ARD and ZDF and partly some other private channels as RTL Television or Pro7), Switzerland (TSI and SSR; now is available free-to-air anywhere in HDTV the Hi-Def channel HD suisse), Italy (through mainly the Satellite broadcasting platform SKY Italia - in fact from march of 2008 SKY Italia will pass all of its channel of Cinema category in 16:9, changing the utility of relative channel SKY Cinema 16:9 - and sometimes Rai Sport Satellite), Greece (SKAI[1]), and in other countries. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located This article is about the country For a topic outline on this subject see List of basic France topics. for the motorway in Tenerife Spain see TF1 Motorway, for the WWI aircraft Sopwith Camel#(Trench Fighter T France Télévisions (fʁɑ̃s televiʒjɔ̃ is the French public national television broadcaster NRJ 12 is a French television network It is available through Digital terrestrial television " TNT " Germany, officially the Federal Republic of Germany ( ˈbʊndəsʁepuˌbliːk ˈdɔʏtʃlant is a Country in Central Europe. Zweites Deutsches Fernsehen ("Second German Television" ZDF, is a public service German Television channel based in Mainz. RTL (formerly RTL plus) is a German commercial Television station distributed via cable and satellite along with DVB-T ProSieben is a commercial Television station in Germany distributed to a large extent via cable and satellite along with DVB-T Switzerland (English pronunciation; Schweiz Swiss German: Schwyz or Schwiiz Suisse Svizzera Svizra officially the Swiss Confederation High-definition television (HDTV is a Digital television Broadcasting system with higher resolution than traditional television systems (standard-definition HD suisse is a 24-hour high-definition television channel operated by the Swiss broadcaster SRG SSR idée suisse. Italy (Italia officially the Italian Republic, (Repubblica Italiana is located on the Italian Peninsula in Southern Europe, and on the two largest SKY Italia is an Italian digital Satellite television platform owned by News Corporation launched the 31 july 2003 Greece (Ελλάδα transliterated: Elláda, historically, Ellás,) officially the Hellenic Republic (Ελληνική Δημοκρατία
Comparing two different aspect ratios is arguably difficult. Given the same diagonal, the 4:3 screen offers more area. For CRT-based technology, an aspect ratio that is closer to square is cheaper to manufacture. The same is true for projectors, and other optical devices such as cameras, camcorders, etc. For LCD and Plasma displays, however, the cost is proportional to the area. Therefore, 16:9 screens are cheaper than 4:3 screens with the same diagonal.
Two aspect ratios compared with images using the same diagonal:
4:3 (1. 33:1) | 16:9 (1. 78:1) |
| 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. Friedrich Christian Anton "Fritz" Lang ( December 5, 1890 &ndash August 2, 1976) was an Austrian German - American M is a 1931 German drama - thriller directed by Fritz Lang and written by Lang and his wife Thea von Harbou The Testament of Dr Mabuse ( Das Testament des Dr Mabuse) is a 1933 movie by director Fritz Lang, a sequel to two of his previous works 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. The 405-line Monochrome analogue Television broadcasting system was the first fully electronic television system to be used in regular broadcasting 33 format. |
| 1. 33:1 | 35 mm original silent film ratio, commonly known in TV and video as 4:3. Video is the technology of electronically capturing, Recording, processing storing transmitting and reconstructing a sequence of Still images Also standard ratio for MPEG-2 video compression. MPEG-2 is a standard for "the generic coding of moving pictures and associated audio information" |
| 1. 37:1 | 35 mm full-screen sound film image, nearly universal in movies between 1932 and 1953. Year 1932 ( MCMXXXII) was a Leap year starting on Friday of the Gregorian calendar. Year 1953 ( MCMLIII) was a Common year starting on Thursday (link will display full calendar of the Gregorian calendar. Officially adopted as the Academy ratio in 1932 by AMPAS. The Academy ratio of 1371 is the standard aspect ratio of a frame of 35mm film when used with 4-perf pulldown, and was standardized by The Academy of Motion Picture Arts and Sciences ( AMPAS) is a professional honorary organization ostensibly dedicated to the advancement of the arts and sciences of Motion Still occasionally used. Also standard 16 mm. |
| 1. 43:1 | IMAX format. IMAX (short for Image MAXimum is a Film format created by Canada 's IMAX Corporation that has the capacity to display images of far greater size and Imax productions use 70mm wide film (the same as used for 70mm feature films), but the film runs through the camera and projector sideways. This allows for a physically larger area for each image. |
| 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. Letterboxing is the practice of transferring Widescreen Film to Video formats while preserving the film's original aspect ratio. |
| 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. High-definition television (HDTV is a Digital television Broadcasting system with higher resolution than traditional television systems (standard-definition MPEG-2 is a standard for "the generic coding of moving pictures and associated audio information" |
| 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. Film perforations, also known as perfs, are the holes placed in the Film stock during manufacturing and used for transporting (via Sprockets and claws and Negative pulldown is a characteristic of motion picture film formats |
| 2. 00:1 | Original SuperScope ratio, also used in Univisium. Univisium ( Latin: "unity of images" is a proposed universal film format created by cinematographer Vittorio Storaro, ASC, AIC and his son Fabrizio |
| 2. 20:1 | 70 mm standard. Originally developed for Todd-AO in the 1950s. Todd-AO is an extremely high definition Widescreen Film format developed in the mid 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. Year 1970 ( MCMLXX) was a Common year starting on Thursday (link shows full calendar of the Gregorian calendar. CinemaScope was a Widescreen movie format used from 1953 to 1967 Panavision is a Motion picture equipment company specializing in Cameras and lenses, based in Woodland Hills California. 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 an area slightly taller than standard 4-perf academy aperture, but presents the widest of aspect ratios. ) |
| 2. 39:1 | 35 mm anamorphic from 1970 onwards. Sometimes rounded up to 2. 40:1[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. CinemaScope was a Widescreen movie format used from 1953 to 1967 This was also the aspect ratio of CinemaScope 55. CinemaScope 55 was a large-format version of CinemaScope introduced in 1955, which used a negative size of 55 |
| 2. 59:1 | Cinerama at full height (three specially captured 35 mm images projected side-by-side into one composite widescreen image). Cinerama is the trademarked name for a Widescreen process which works by simultaneously projecting images from three synchronized 35 mm projectors onto a huge deeply-curved |
| 2. 76:1 | MGM Camera 65 (65 mm with 1. Ultra Panavision 70, also known as MGM Camera 65, was the marketing brand used to identify 65/70 mm movies photographed with Panavision Anamorphic optics 25x anamorphic squeeze). Used only on a handful of films between 1956 and 1964, such as Ben-Hur (1959). Year 1956 ( MCMLVI) was a Leap year starting on Sunday (link will display full calendar of the Gregorian calendar. Year 1964 ( MCMLXIV) was a Leap year starting on Wednesday (link will display full calendar of the 1964 Gregorian calendar. Ben-Hur (or Benhur is a 1959 Movie directed by William Wyler, and is the third film version of Lew Wallace 's novel Ben-Hur |
| 4. 00:1 | Polyvision, three 35 mm 1. Polyvision was the name given to a specialized Widescreen Film format devised exclusively for the filming and projection of Abel Gance 's 33 images projected side by side. Used only on Abel Gance's Napoléon (1927). Abel Gance (25 October 1889 - 10 November 1981 was a French Film director, producer, Writer, Actor and editor best Napoléon ( 1927) is an epic silent French Film directed by Abel Gance that tells the story of the rise of Napoleon Year 1927 ( MCMXXVII) was a Common year starting on Saturday (link will display full calendar of the Gregorian calendar. |
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. Home cinema, also called home theater, are entertainment systems that seek to reproduce cinema quality video and audio in a private home As an example, the film Gladiator was released to theaters in the 2. Gladiator is a 2000 Epic film directed by Ridley Scott and starring Russell Crowe, Joaquin Phoenix, Connie Nielsen 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. Super 35 (originally known as Superscope 235) is a Motion picture Film format that uses exactly the same film stock as standard 35 mm film, but 39:1, it was also broadcast without the matte altering the aspect ratio to the television standard of 1. For the technique of creating backgrounds see Matte painting. 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 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. Pan and scan is one method of adjusting Widescreen film images so that they can be shown within the proportions of a Standard definition 43 aspect ratio Open matte is a filming technique that involves matting out the top and bottom of the film frame in the Movie projector (known as a soft matte) for the Widescreen 85:1 film to open up the full 1. 33:1 frame.
Multiple aspect ratios create additional burdens on filmmakers and consumers, and confusion among TV broadcasters. Windowboxing (also called the "postage stamp effect" occurs when the Aspect ratio of a film is such that the Letterbox effect and pillarbox effect 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). Windowboxing (also called the "postage stamp effect" occurs when the Aspect ratio of a film is such that the Letterbox effect and pillarbox effect 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 a 4:3 image of the commercial with 2 sets of black stripes, vertical and horizontal (windowboxing or the postage stamp effect). Windowboxing (also called the "postage stamp effect" occurs when the Aspect ratio of a film is such that the Letterbox effect and pillarbox effect Letterboxing is the practice of transferring Widescreen Film to Video formats while preserving the film's original aspect ratio. 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. Letterboxing is the practice of transferring Widescreen Film to Video formats while preserving the film's original aspect ratio.
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. SCART (from Syndicat des Constructeurs d'Appareils Radiorécepteurs et Téléviseurs)
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. David Llewelyn Wark "D W" Griffith (January 22 1875 &ndash July 23 1948 was a premier pioneering Academy Award -winning American Film director. 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.
Common aspect ratios in still photography include 4:3 (1. 33) used by most point-and-shoot digital cameras; 3:2 (1. A point-and-shoot camera, also called a compact camera, is a Still camera designed primarily for simple operation 5) used by 35mm film, APS-C ("classic" mode) and most DSLRs; 1. A digital single-lens reflex camera ( digital SLR or DSLR) is a Digital camera that uses an automatic mirror system and Pentaprism 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. Advanced Photo System ( APS) is a Film format for still Photography.
Common print sizes in the U.S. (in inches) include 4x6 (1. The United States of America —commonly referred to as the Inches redirects here To see the Les Savy Fav album see Inches. 5), 5x7 (1. 4), 4x5 and 8x10 (1. 25), and 11x14 (1. 27); large-format cameras typical use one of these aspect ratios. Large format describes large Photographic films large cameras View cameras (including Pinhole cameras and processes that use a film or digital sensor Medium-format cameras typically have format designated by nominal sizes in centimeters (6x6, 6x7, 6x9, 6x4. This page is about medium-sized film formats For formats of a different Medium, see Format disambiguation A centimetre ( American spelling: centimeter, symbol cm) is a unit of Length in the Metric system, equal to one hundredth 5), but these numbers should not be interpreted as exact in computing aspect ratios.