This keyer lets you use the red, green or blue channel as a basis for a luma key. It was designed to tackle the difficulties of keying hair.
BM_LumaKeyer
Updated: 5 June 2011
Author: BenMcEwan
Compatible Nuke versions: 6.2 or later
Compatibility: Linux, Mac, Windows
Provided you have a bit of contrast between your subject and the background in one of your Red, Green or Blue channels you'll be able to get a fairly decent luma key. You basically use the graph to best-define what part of your image is the foreground, and what part is the background. From there, you can use the Foreground/Background controls to create your matte!