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ITU-R BT.1886

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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).

Definition

BT.1886 EOTF is as follows:

L = a ( max [ ( V + b ) , 0 ] ) γ {\displaystyle L=a(\max)^{\gamma }} where

  • L {\displaystyle L} is the screen luminance, in cd/m.
  • V {\displaystyle V} is the input video signal level, in the range [ 0 , 1 ] {\displaystyle \left} .
  • γ {\displaystyle \gamma } is the exponent of the power function and equal to 2.4
  • a = ( L W 1 / γ − L B 1 / γ ) γ {\displaystyle a=({L_{W}}^{1/\gamma }-{L_{B}}^{1/\gamma })^{\gamma }} is the variable for user gain (legacy “contrast” control)
  • b = L B 1 / γ L W 1 / γ − L B 1 / γ {\displaystyle b={\frac {{L_{B}}^{1/\gamma }}{{L_{W}}^{1/\gamma }-{L_{B}}^{1/\gamma }}}} is the variable for user black level lift (legacy “brightness” control)
  • L W {\displaystyle L_{W}} is the screen luminance for white, in cd/m.
  • L B {\displaystyle L_{B}} is the screen luminance for black, in cd/m.

According to ITU, for a better match, L B {\displaystyle L_{B}} can be set to 0.1 for moderate black level settings (e.g. 0.1 cd/m) or to 0 for lower black levels (e.g. 0.01 cd/m).

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

See also

References

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