lift-gamma-gain color correction formula with blender compositing

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I got lately interest in Lift/Gamma/Gain formula for some personal project, I thought I would share some of the informations I found.

What does Lift/Gamma/Gain ?

Lift/Gamma/Gain is actually is a really nice approach for color correction in my opinion. Lift/Gamma/Gain are actually controlling the Shadows/Mid-tones/High-tones of your picture with the ability to offset the colors.
This combine with saturation and exposure could give a powerful tool for color correction. This is the kind of tool you’ll find in plug-in such as Magic Bullet Colorista from Red Giant Software or professional hardware as Black Magic DaVinci

Stu Maschwitz from Prolost did a nice tutorial on how to use his Colorista plug-in

Red Giant TV Episode 22: Creating a Summer Blockbuster Film Look from Stu Maschwitz on Vimeo.

Mirror of http://www.redgiantsoftware.com/videos/redgianttv/item/23/

Lift/Gamma/Gain formula

outputColor = (gainColor*(inputColor+liftColor*(1-inputColor)))^(1/gammaColor)

This has to be done for each channel color for each pixels of your picture.

To make some test of this formula I did use Blender’s compositing and its “Math” node which was pretty useful . This operation is useless since it is terribly slow using nodes and it’s already implemented in the Sequencer (properties of the strip), but it’s just for the test !