title: Lift, Gamma, and Gain (GLSL)
media types:
Video
description: A simple lift/gamma/gain effect, used for color grading.
version: 1
creator: Steinar H. Gunderson
copyright: Dan Dennedy
license: GPLv2
Very roughly speaking, lift=shadows, gamma=midtones and gain=highlights, although all parameters affect the entire curve. Mathematically speaking, it is a bit unusual to look at gamma as a color, but it works pretty well in practice. The classic formula is: output = (gain * (x + lift * (1-x)))^(1/gamma). The lift is actually a case where we actually would not want linear light; since black by definition becomes equal to the lift color, we want lift to be pretty close to black, but in linear light that means lift affects the rest of the curve relatively little. Thus, we actually convert to gamma 2.2 before lift, and then back again afterwards. (Gain and gamma are, up to constants, commutative with the de-gamma operation.)
title: Lift Red
type: float
readonly: no
required: no
minimum: 0.0
default: 0.0
title: Lift Green
type: float
readonly: no
required: no
minimum: 0.0
default: 0.0
title: Lift Blue
type: float
readonly: no
required: no
minimum: 0.0
default: 0.0
title: Gamma Red
type: float
readonly: no
required: no
minimum: 0.0
default: 1.0
title: Gamma Green
type: float
readonly: no
required: no
minimum: 0.0
default: 1.0
title: Gamma Blue
type: float
readonly: no
required: no
minimum: 0.0
default: 1.0
title: Gain Red
type: float
readonly: no
required: no
minimum: 0.0
default: 1.0
title: Gain Green
type: float
readonly: no
required: no
minimum: 0.0
default: 1.0
title: Gain Blue
type: float
readonly: no
required: no
minimum: 0.0
default: 1.0
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