The Math of Color Grading in Nuke

In this video we'll take a close look at the simple mathematical functions behind color grading operations in Nuke. We will only discuss operations that affect brightness, or value of an image. We'll save the more complex discussion of color and hue for a future video.

00:00 - Introduction
01:00 - Scene-linear and why it's important
02:30 - What is a linear function
04:30 - How the Grade node works
06:40 - Power functions and gamma
10:16 - Adjusting exposure in stops
12:10 - Compressing brightness with a logarithmic function
24:44 - How to take a complement with the invert node
25:44 - Keep your Toe under control
28:18 - Partitioning brightness ranges with ColorCorrect
30:56 - Make your own curves with the ColorLookup
30:31 - What the heck is RolloffContrast useful for anyway?!
34:48 - Histogram and why Nuke is not Photoshop

For a more detailed look at using the Grade node, please watch Frank Reuter's excellent presentation on Color Correction - NUKE Basic Workflows: https://vimeo.com/76514569

The Desmos plots I show in this video are available here if you would like to play around with them:
Linear Equation in Slope Intercept Form: https://www.desmos.com/calculator/ibo...
Slope Intercept Calculation: https://www.desmos.com/calculator/nvp...
Grade Node Math: https://www.desmos.com/calculator/gq1...
Power Function (Gamma): https://www.desmos.com/calculator/pcc...
Log Function: https://www.desmos.com/calculator/9j1...
Log2Shaper Function: https://www.desmos.com/calculator/cig...

And here are some Wikipedia links for further reading:
https://en.wikipedia.org/wiki/Linear_...
https://en.wikipedia.org/wiki/Proport...)
https://en.wikipedia.org/wiki/Complem...)

And a few other links I discuss in the video:
Friends don't let friends view scene-linear imagery without an s-shaped view transform: https://cinematiccolor.org
CinematicColor v2 - Common RGB Colorspaces : https://nick-shaw.github.io/cinematic...

The image I am using to demonstrate scene-linear and an s-shaped view transform is available at cinematography.net here: https://www.cinematography.net/Valvul...

And here's the nuke script if you want to play with it: https://codeshare.io/zyMb7D