Apple Shake 4 - Manual (Page 683)

Chapter 24 Keying 683
Because ColorReplace puts white in the SourceColor area of the alpha channel, use the
Invert node to invert the image for the Over node.
The initial settings yield blue fringes. In the ColorReplace parameters, set satFalloff to 1
to correct this. Also, if pure black or pure white pixels start to show transparent, set the
valRange and valFalloff numbers to approximately .2 and .5.
You can see there is some crunchiness, particularly in the hair. This demonstrates why
ColorReplace is usually used to pull a key to mask other operations such as color
correctors, rather than the actual composite. There are examples of using ColorReplace
in the “Blue and Green Spill Suppression” section below.
Combining Keyers
You get the most flexibility when you combine keyers. Both Primatte and Keylight allow
you to input a holdout matte. There are at least three typical ways of combining keys:
• Use the Primatte or Keylight holdout matte input.
• Use the Primatte arithmetic operator.
• Use the Max, IAdd, IMult, Over, Inside, or Outside node.