ITU-R BT.1886

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:

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

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).
 * $$L$$ 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 2.4
 * $$a = ({L_W}^{1/\gamma} - {L_B}^{1/\gamma})^{\gamma}$$ is the variable for user gain (legacy “contrast” control)
 * $$b = \frac {{L_B}^{1/\gamma}} {{L_W}^{1/\gamma} - {L_B}^{1/\gamma}}$$ is the variable for user black level lift (legacy “brightness” control)
 * $$L_W$$ is the screen luminance for white, in cd/m2.
 * $$L_B$$ is the screen luminance for black, in cd/m2.

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