ct ratio defined by the Sinema Sanatları ve Bilimleri Akademisi as a standard after the advent of optical sound-on-film. By having TV match this aspect ratio, movies originally photographed on 35 mm film could be satisfactorily viewed on TV in the early days of the medium (i.e. the 1940s and the 1950s). When sinema attendance dropped, film endüstrisini televizyondan farklılaştırmak amacıyla Hollywood geniş ekran çerçeve oranlarını (daha önce bahsedilen 1.85:1 oranı gibi) oluşturdu. Fakat However since the start of the 21st century broadcasters worldwide are phasing out the 4:3 standard entirely, as technology started to favour the 16:9/16:10 aspect ratio of all modern HD TV sets, computer monitors as well as broadcast cameras.

16:9 (1.7:1) (genellikle ""On Altıya Dokuz"" olarak adlandırılan) HDTV, standart dijital televizyon ve PALplus analog geniş ekran televizyonun uluslararası standart formatıdır. Japonya'nın Hi-Vision'ı aslında 5:3 oranla başladı, fakat uluslararası standartlar grubu daha geniş bir 5⅓'e 3 oranını (=16:9) tanıtınca dönüştürüldü. Çok sayıda dijital video kamerası 16:9'da kayıt edebilme yeteneğine sahip ve 16:9 yalnızca geniş ekran çerçeve oranı doğallıkla is the only widescreen aspect ratio natively supported by DVD standardı tarafından doğallıkla desteklenen . DVD producers can also choose to show even wider ratios such as 1.85:1 and 2.39:1 within the 16:9 DVD frame by hard matting or adding black bars within the image itself. Some films which were made in a 1.85:1 aspect ratio, such as the U.S.-Italian co-production "Man of La Mancha", fit quite comfortably onto a 1.7:1 HDTV screen and have been issued anamorphically enhanced on DVD without the black bars.

Often, screen specifications are given by their diagonal length. The following formulae can be used to find the height ("h"), width ("l" for "length") and area ("A"), where "r" stands for ratio and "d" for diagonal length.

formula_1

This article primarily addresses the aspect ratio of images "as displayed," which is more formally referred to as the display aspect ratio (DAR). In digital images, there is a distinction with the (SAR), which is the ratio of pixel dimensions. If an image is displayed with square pixels, then these ratios agree; if not, then non-square, "rectangular" pixels are used, and these ratios disagree. The aspect ratio of the pixels themselves is known as the pixel aspect ratio (PAR) – for square pixels this is 1:1 – and these are related by the identity:
Rearranging (solving for PAR) yields:
For example, a 640 × 480 VGA image has a SAR of 640/480 = 4:3, and if displayed on a 4:3 display (DAR = 4:3), has square pixels, hence a PAR of 1:1. By contrast, a 720 × 576 D-1 PAL image has a SAR of 720/576 = 5:4, but is displayed on a 4:3 display (DAR = 4:3), so by this formula it would have a PAR of (4:3)/(5:4) = 16:15.

However, because standard definition digital video was originally based on digitally sampling analog television, the 720 horizontal pixels actually capture a slightly wider image to avoid loss of the original analog picture. In actual images, these extra pixels are often partly or entirely black, as only the center 704 horizontal pixels carry actual 4:3 or 16:9 image. Hence, the actual pixel aspect ratio for PAL video is a little different from that given by the formula, specifically 12:11 for PAL and 10:11 for NTSC. For consistency, the same effective pixel aspect ratios are used even for standard definition digital video originated in digital form rather than converted from analog. For more details refer to the main article.

In analog images such as film there is no notion of pixel, nor notion of SAR or PAR, and "aspect ratio" refers unambiguously to DAR. Actual displays do not generally have non-square pixels, though digital sensors might; they are rather a mathematical abstraction used in resampling images to convert between resolutions.

Non-square pixels arise often in early digital TV standards, related to digitalization of analog TV signals – whose horizontal and vertical resolutions differ and are thus best described by non-square pixels – and also in some digital videocameras and computer display modes, such as Color Graphics Adapter (CGA). Today they arise particularly in transcoding between resolutions with different SARs.

DAR is also known as image aspect ratio and picture aspect ratio, though the latter can be confused with "pixel" aspect ratio.

Comparing two different aspect ratios poses some subtleties – when comparing two aspect ratios, one may compare images with equal height, equal width, equal diagonal, or equal area. More amorphous questions include whether particular subject matter has a natural aspect ratio (panoramas being wide, full-length images of people being tall), or whether a particular ratio is more or less aesthetically pleasing – the golden ratio (~1.618) is seen as especially pleasing. Of common display formats, (8/5) is the closest to the golden ratio, and 15:9 is the closest film format.

Given the same diagonal, the 4:3 screen offers more (over 12%) area, because it is closer to square (which maximizes area given a diagonal). 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 more related to the area, so producing wider and shorter screens yields the same advertised diagonal but lower area, and hence is more profitable.

The following compares crops of a given image at 4:3 and 16:9, with different parameters equal; note that in terms of "subject," the squarer aspect ratio emphasizes the public square, while the wider aspect ratio emphasizes the wide building.




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 altering the aspect ratio to the television standard of 1.3:1. 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 1.3:1 (historically), or (with the advent of widescreen television sets) 1.7:1 aspect ratio. 1.3:1 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 1.3:1 frame. Another name for it is "prescaled" aspect ratio".

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 a 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. Active Format Description is a mechanism used in digital broadcasting to avoid this problem. It is also common that a 4:3 image is stretched horizontally to fit a 16:9 screen to avoid pillar boxing but distorts the image so subjects appear short and fat.

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 – Widescreen signaling 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.

Common aspect ratios in still photography include:


Many digital still cameras offer user options for selecting multiple image aspect ratios. Some achieve this through the use of multi-aspect sensors (notably Panasonic), while others simply crop their native image format to have the output match the desired image aspect ratio.

is the classic square image, and is available as a choice in some digital still cameras, and harkens back to the days of film cameras when the square image was somewhat popular with photographers using medium format cameras shooting 120 film rolled onto spools. The 6 × 6 cm image size was the classic 1:1 format in the recent past. 120 film can still be found and used today.

is used by most digital point-and-shoot cameras, Four Thirds system, Micro Four Thirds system cameras and medium format 645 cameras. The 4:3 digital format popularity was developed to match the then prevailing digital displays of the time, 4:3 computer monitors.

The next several formats have their roots in classic film photography image sizes, both the classic 35 mm film camera, and the multiple format Advanced Photo System (APS) film camera. The APS camera was capable of selecting any of three image formats, APS-H ("High Definition" mode), APS-C