Editing Gamma correction (section)

==Film photography==
{{anchor|Photography}}
{{main|Sensitometry}}
[[File:Foto-wiki-Characteristic-Curve.svg|thumb|Characteristic curve of a [[photographic film]]. The slope of its linear section is called the gamma of the film.]]
When a [[photographic film]] is exposed to light, the result of the exposure can be represented on a graph showing log of [[Exposure (photography)|exposure]] on the horizontal axis, and density, or negative log of transmittance, on the vertical axis. For a given film formulation and processing method, this curve is its [[Sensitometry|characteristic]] or [[Hurter and Driffield|Hurter–Driffield curve]].<ref>Kodak, "Basic sensitometry and characteristics of film" [http://motion.kodak.com/motion/uploadedFiles/US_plugins_acrobat_en_motion_newsletters_filmEss_06_Characteristics_of_Film.pdf] {{Webarchive|url=https://web.archive.org/web/20120820051450/http://motion.kodak.com/motion/uploadedFiles/US_plugins_acrobat_en_motion_newsletters_filmEss_06_Characteristics_of_Film.pdf|date=2012-08-20}}: "A characteristic curve is like a film's fingerprint."</ref><ref name=kodak>{{cite web |url=http://www.kodak.com/global/en/professional/support/techPubs/f4017/f4017.jhtml |title=Kodak Professional Tri-X 320 and 400 Films |date=May 2007 |publisher=[[Eastman Kodak Company]] |format=PDF |access-date=2015-01-03 |archive-date=2009-08-02 |archive-url=https://web.archive.org/web/20090802104632/http://www.kodak.com/global/en/professional/support/techPubs/f4017/f4017.jhtml |url-status=dead }}</ref> Since both axes use logarithmic units, the slope of the linear section of the curve is called the gamma of the film. Negative film typically has a gamma less than 1;<ref name=kodak/><ref name="portra160">{{cite web |title=KODAK PROFESSIONAL PORTRA 160 Film |url=http://imaging.kodakalaris.com/sites/prod/files/files/products/e4051_portra_160.pdf |website=imaging.kodakalaris.com |publisher=kodak |access-date=29 January 2019}}</ref> positive film (slide film, reversal film) typically has a gamma with absolute value greater than 1.<ref name="kodachromeProfessionalFilm">{{cite web |title=KODACHROME 25, 64, and 200 Professional Film |url=http://wwwuk.kodak.com/global/en/professional/support/techPubs/e55/e55.pdf |website=wwwuk.kodak.com |publisher=Kodak |access-date=29 January 2019}}</ref>