ITU-R BT.1886 explained

ITU-R BT.1886 is the reference EOTF of SDR-TV. It is a gamma 2.4 transfer function (a power law with a 2.4 exponent) considered as a satisfactory approximation of the response characteristic of CRT to electrical signal. It has been standardized by ITU in March 2011. It is used for Rec. 709 (HD-TV) and Rec. 2020 (UHD-TV).^{[1] [2]}

Definition

BT.1886 EOTF is as follows:

L = a ( max [(V + b), 0 ]) ^{\gamma} whereL is the screen luminance, in cd/m². V is the input video signal level, in the range \left[ 0 , 1 \right] .\gamma is the exponent of the power function and equal to 2.4a = ({L ^{1 /\gamma} _{W}} - {L ^{1 /\gamma} _{B}} ) ^{\gamma} is the variable for user gain (legacy “contrast” control)b = ({L _{B})/(^{1/\gamma}) } is the variable for user black level lift (legacy “brightness” control) L _{W} is the screen luminance for white, in cd/m². L _{B} is the screen luminance for black, in cd/m². According to ITU, for a better match, L _{B} can be set to 0.1 for moderate black level settings (e.g. 0.1 cd/m²) or to 0 for lower black levels (e.g. 0.01 cd/m²).

An alternative EOTF has also been provided by ITU for the cases a more precise match of CRT characteristics is required.

See also

• Gamma correction
• Transfer functions in imaging

Notes and References

1. Web site: BT.1886 : Reference electro-optical transfer function for flat panel displays used in HDTV studio production. 2021-11-07. www.itu.int.
2. Web site: BT.2020 : Parameter values for ultra-high definition television systems for production and international programme exchange. 2021-11-07. www.itu.int.