standard-dynamic-range video

Conventional gamma curves:

• Opto-electronic transfer function (OETF):
• Rec. 601 (analog video signals in SD-TV digital video form){{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}}{{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}}
• Rec. 709 (HD-TV)
• Rec. 2020 (UHD-TV)
• sRGB
• Electro-optical transfer function (EOTF):
• ITU-R BT.1886 (SDR-TV)
• sRGB (monitors, printers, World Wide Web){{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=}}

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. An example of a conventional gamma curve would be Rec. 601:

$E=\backslash begin\{cases\}$

4.500L & L < 0.018\\

1.099 L^{0.45} - 0.099 & L \ge 0.018

\end{cases}

ITU-R Recommendation BT.1886 describe the reference EOTF of SDR. It's a gamma curve representing the response of CRT to video signal. It has been published by ITU in 2011.

A transfer function that is closer to Weber's law allows for a larger dynamic range, at the same bit depth, than a conventional gamma curve.{{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}} HDR standards such as hybrid log–gamma (HLG) and SMPTE ST 2084 allow for a larger dynamic range by using a different transfer function. HLG is compatible with SDR displays.{{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}}

In some cases the term SDR is also used with a meaning including the standard color gamut (i.e. Rec.709 / sRGB color primaries). HDR uses wide color gamut (WCG) such as Rec. 2020 or DCI-P3 color primaries.{{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}}

The dynamic range that can be perceived by the human eye in a single image is around 14 stops. SDR video with a conventional gamma curve and a bit depth of 8-bits per sample has a dynamic range of about 6 stops, assuming a luminance quantisation threshold of 5% is used. 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.

While conventional gamma curves are useful for low light and are compatible with CRT displays, they can only represent a limited dynamic range.{{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}} 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). However, current displays are often far more capable than CRT's limits. On such displays, higher brightness and wider color gamut can be displayed by adjusting and trying to enhance the SDR picture. HDR is however required for the creative intents to be preserved.

{{Reflist}}

• [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