Editing Gamma correction (section)

==Standard gammas==

===Analog TV===
Output to CRT-based television receivers and monitors does not usually require further gamma correction. The standard video signals that are transmitted or stored in image files incorporate gamma compression matching the gamma expansion of the CRT (although it is not the exact inverse). 
For television signals, gamma values are fixed and defined by the analog video standards. [[CCIR System M]] and [[CCIR System N|N]], associated with [[NTSC]] color, use gamma 2.2;  systems [[CCIR System B|B]]/[[CCIR System G|G]], [[CCIR System H|H]], [[CCIR System I|I]], [[CCIR System D|D]]/[[CCIR System K|K]], [[CCIR System K1|K1]], [[CCIR System L|L]] and M associated with [[PAL]] or [[SECAM]] color use gamma 2.8.<ref>{{cite book|url=https://search.itu.int/history/HistoryDigitalCollectionDocLibrary/4.283.43.en.1030.pdf|title=Reports of the CCIR, 1990: Also Decisions : XVIIth Plenary Assembly, Dusseldorf|year=1990|publisher=International Radio Consultative Committee|section=11A: Characteristics of systems for monochrome and color television}}</ref><ref name=":0">{{Cite book |url=https://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.470-6-199811-S!!PDF-E.pdf#page=9 |title=Rec. ITU-R BT.470-6 - CONVENTIONAL TELEVISION SYSTEMS |publisher=ITU-R |year=1998 |pages=9}}</ref>

===Computer displays===
{{Further|sRGB#Transformation}}
In most computer display systems, images are encoded with a gamma of about 0.45 and decoded with the reciprocal gamma of 2.2. A notable exception, until the release of Mac OS X 10.6 (Snow Leopard) in September 2009, were [[Macintosh]] computers, which encoded with a gamma of 0.55 and decoded with a gamma of 1.8. In any case, [[binary file|binary]] data in still image files (such as [[JPEG]]) are explicitly encoded (that is, they carry gamma-encoded values, not linear intensities), as are motion picture files (such as [[MPEG]]). The system can optionally further manage both cases, through [[color management]], if a better match to the output device gamma is required.

[[File:SRGB gamma.svg|thumb|227px|Plot of the [[sRGB]] standard gamma-expansion nonlinearity in red, and its local gamma value (slope in log–log space) in blue. The local gamma rises from 1 to about 2.2.]]
The [[sRGB color space]] standard used with most cameras, PCs, and printers does not use a simple power-law nonlinearity as above, but has a decoding gamma value near 2.2 over much of its range, as shown in the plot to the right/above. Below a compressed value of 0.04045 or a linear intensity of 0.00313, the curve is linear (encoded value proportional to intensity), so {{nowrap|1=''γ'' = 1}}. The dashed black curve behind the red curve is a standard {{nowrap|1=''γ'' = 2.2}} power-law curve, for comparison.

Gamma correction in computers is used, for example, to display a gamma = 1.8 Apple picture correctly on a gamma = 2.2 PC monitor by changing the image gamma. Another usage is equalizing of the individual color-channel gammas to correct for monitor discrepancies.