ITU-R BT.1886 is the reference transformation to convert a picture or video signal into the linear light output (EOTF) for the display 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:
where
is the screen luminance, in cd/m2. is the input video signal level, in the range . is the exponent of the power function and equal to 2.4 is the variable for user gain (legacy “contrast” control) is the variable for user black level lift (legacy “brightness” control) is the screen luminance for white, in cd/m2. is the screen luminance for black, in cd/m2. According to ITU, for a better match, 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
References