View source for Standard-dynamic-range video

{{Short description|Video with a dynamic range that was standard before high-dynamic-range video}}
'''Standard-dynamic-range video''' ('''SDR video''') is a [[video]] technology which represents light intensity based on the [[brightness]], [[Contrast (vision)|contrast]] and [[color]] characteristics and limitations of a [[cathode ray tube]] (CRT) display.<ref name=":1">{{Cite web|title=HDR (High Dynamic Range) on TVs explained|url=https://www.flatpanelshd.com/focus.php?subaction=showfull&id=1435052975|access-date=2021-04-25|website=FlatpanelsHD}}</ref> SDR video is able to represent a video or picture's colors with a maximum [[luminance]] around 100 [[Candela per square metre|cd/m<sup>2</sup>]], a black level around 0.1 [[Candela per square metre|cd/m<sup>2</sup>]] and [[Rec. 709|Rec.709]] / [[sRGB]] [[Gamut|color gamut]].<ref name=":1" /><ref name=":6">{{Cite web|title=ITU-R Report BT.2390 - High dynamic range television for production and international programme exchange|url=https://www.itu.int:443/en/publications/ITU-R/Pages/publications.aspx|access-date=2021-04-29|website=ITU|language=en-US}}</ref> It uses the [[Gamma correction|gamma curve]] as its [[electro-optical transfer function]].<ref name=":1" /><ref name=":0">{{Cite web|title=BT.1886 : Reference electro-optical transfer function for flat panel displays used in HDTV studio production|url=https://www.itu.int/rec/R-REC-BT.1886-0-201103-I/en|access-date=2021-04-24|website=www.itu.int}}</ref>

The first CRT [[television set]]s were manufactured in 1934 and the first color CRT television sets were manufactured in 1954.<ref name="15GP22ColorCRT2016">{{cite news|title=15GP22 Color CRT|publisher=Early Television Museum|url=http://www.earlytelevision.org/15GP22.html|accessdate=2016-02-02}}</ref><ref name="EarlyTelevisionGallery2016">{{cite news|title=Early Electronic Television|publisher=Early Television Museum|url=http://www.earlytelevision.org/telefunken.html|accessdate=2016-02-02}}</ref> The term "standard-dynamic-range video" was adopted to distinguish SDR video from [[high-dynamic-range video]] (HDR video), a new technology that was developed in the 2010s to overcome SDR's limits.<ref name=":1" /><ref>{{Cite web|title=CES 2014: Dolby Vision promises a brighter future for TV, Netflix and Xbox Video on board|url=https://www.expertreviews.co.uk/go/27453|access-date=2021-04-24|website=Expert Reviews|date=6 January 2014 |language=en}}</ref>

==Technical details==

=== Transfer function ===
Conventional [[Gamma correction|gamma curves]]:

* [[Opto-electronic transfer function]] (OETF):
** [[Rec. 601]] ([[analog video]] signals in [[Standard-definition television|SD-TV]] [[digital video]] form)<ref>{{cite web |title=BT.601: Studio encoding parameters of digital television for standard 4:3 and wide screen 16:9 aspect ratios |url=https://www.itu.int/rec/R-REC-BT.601/ |publisher=ITU}}</ref><ref name="ReportHDR2015SMPTE">{{cite news|title=Study Group Report High-Dynamic-Range (HDR) Imaging Ecosystem|publisher=Society of Motion Picture and Television Engineers|url=https://www.smpte.org/standards/reports|accessdate=2016-02-02}}</ref>
** [[Rec. 709]] ([[High-definition television|HD-TV]])<ref name="ReportHDR2015SMPTE" />
** [[Rec. 2020]] ([[Ultra-high-definition television|UHD-TV]])
** [[sRGB]]
* [[Electro-optical transfer function]] (EOTF):
** [[ITU-R BT.1886]] (SDR-TV)<ref name=":0" />
** [[sRGB]] (monitors, printers, [[World Wide Web]])<ref name="orig_pub">{{cite web |author1=Michael Stokes |author2=Matthew Anderson |author3=Srinivasan Chandrasekar |author4=Ricardo Motta |date=November 5, 1996 |title=A Standard Default Color Space for the Internet – sRGB, Version 1.10 |url=https://www.w3.org/Graphics/Color/sRGB.html |archive-url= |archive-date= |access-date= |website=}}</ref>
The linear part of the conventional gamma curve was used to limit camera noise in low light video but is no longer needed with [[high dynamic range]] (HDR) cameras.<ref name="ReportHDR2015SMPTE" /> An example of a conventional gamma curve would be Rec. 601:

<math>E=\begin{cases}
4.500L & L < 0.018\\
1.099 L^{0.45} - 0.099 & L \ge 0.018
\end{cases}
</math>

[[ITU-R BT.1886|ITU-R Recommendation BT.1886]] describe the reference [[EOTF]] of SDR.<ref name=":0" /> It's a [[Gamma correction|gamma curve]] representing the response of [[Cathode-ray tube|CRT]] to video signal.<ref name=":0" /> It has been published by [[International Telecommunication Union|ITU]] in 2011.<ref name=":0" />

A [[transfer function]] that is closer to [[Weber's law]] allows for a larger dynamic range, at the same [[Color depth|bit depth]], than a conventional gamma curve.<ref name="DisplayHDR2015BBC">{{cite news|author=T. Borer|author2=A. Cotton|title=A "Display Independent" High Dynamic Range Television System|publisher=[[BBC]]|url=http://downloads.bbc.co.uk/rd/pubs/whp/whp-pdf-files/WHP309.pdf|accessdate=2016-02-02}}</ref> [[High-dynamic-range video|HDR]] standards such as [[hybrid log–gamma]] (HLG) and [[SMPTE ST 2084]] allow for a larger dynamic range by using a different [[Transfer functions in imaging|transfer function]].<ref name="DisplayHDR2015BBC" /><ref name="DolbyVision2016Dolby" /> [[Hybrid log–gamma|HLG]] is compatible with SDR displays.<ref name="IBCDemo2015EBU">{{cite news|title=High Dynamic Range|publisher=[[European Broadcasting Union]]|url=https://tech.ebu.ch/docs/events/IBC2015/IBC_Fact_Sheet_HDR_Demo_Final.pdf|accessdate=2015-11-01}}</ref>

=== Color gamut ===
In some cases the term SDR is also used with a meaning including the standard [[Gamut|color gamut]] (i.e. [[Rec. 709|Rec.709]] / [[sRGB]] [[Primary color|color primaries]]).<ref name=":1" /> [[High-dynamic-range video|HDR]] uses [[Wide Color Gamut|wide color gamut]] (WCG) such as [[Rec. 2020]] or [[DCI-P3]] color primaries.<ref name=":1" /><ref name=":2">{{Cite web|title=BT.2100 : Image parameter values for high dynamic range television for use in production and international programme exchange|url=https://www.itu.int/rec/R-REC-BT.2100|access-date=2021-04-25|website=www.itu.int}}</ref>

=== Dynamic range ===
The [[dynamic range]] that can be perceived by the [[human eye]] in a single image is around 14 [[Exposure value|stops]].<ref name="DisplayHDR2015BBC" /> SDR video with a conventional gamma curve and a [[color depth|bit depth]] of 8-bits per sample has a dynamic range of about 6 stops, assuming a [[luminance quantisation threshold]] of 5% is used.<ref name="DisplayHDR2015BBC" /> A threshold of 5% is used in the paper (instead of the standard 2% threshold) to allow for the typical display being dimmer than ideal. Professional SDR video with a bit depth of 10-bits per sample has a dynamic range of about 10 stops.<ref name="DisplayHDR2015BBC" />

==Displaying SDR video on modern displays==
While conventional [[Gamma correction|gamma curves]] are useful for low light and are compatible with [[Cathode-ray tube|CRT]] displays, they can only represent a limited [[dynamic range]].<ref name=DisplayHDR2015BBC/><ref name="DolbyVision2016Dolby">{{cite news|title=Dolby Vision White Paper|publisher=[[Dolby Laboratories]]|url=http://www.dolby.com/us/en/technologies/dolby-vision/dolby-vision-white-paper.pdf|accessdate=2016-02-02}}</ref> Standards require SDR to be viewed on a display with the same characteristics as a CRT (i.e. 100 nits peak [[brightness]], gamma curve, [[Rec. 709]] color primaries).<ref name=":1" /><ref name=":0" /> However, current displays are often far more capable than CRT's limits.<ref name=":1" /> On such displays, higher brightness and wider color gamut can be displayed by adjusting and trying to enhance the SDR picture.<ref name=":1" /> [[High-dynamic-range video|HDR]] is however required for the creative intents to be preserved.<ref name=":1" />

==References==
{{Reflist}}

==External links==
*[https://www.itu.int/rec/R-REC-BT.1886/ ITU-R Recommendation BT.1886]

{{Dynamic range color representation}}

[[Category:Display technology]]
[[Category:Television technology]]
[[Category:Color]]
[[Category:High dynamic range]]