Gamma Curve

For the gamma curve, this function is used:

Light = ((Signal + Offset) / (1 + Offset)) ^ Gamma

where Offset = ((1 / OnOffCR) ^ (1 / Gamma)) / (1 - ((1 / OnOffCR) ^ (1 / Gamma))).

Basically, Offset accounts for the black-level error. In particular, if Signal is 0, then Light becomes (1/OnOffCR), which is the black level.

Signal is within the range of 0 to 1, so Light is within the range of (1/OnOffCR) to 1.

For example, if Gamma is 2.22, and OnOffCR is 210, then Offset becomes 0.099, resulting in this function:

Light = ((Signal + 0.099) / 1.099) ^ 2.22

which happens to be nearly identical to the inverse of the non-linear portion of the Rec. 709 transfer function.

This web page was created by Erik Garci.