Apple Shake 4 Tutorials - Manual (Page 182)

182 Chapter 5 Using Keylight
To test the effect of the holdout matte:
m In the lower portion of the Keylight1 parameters, expand the plumbing subtree, then
enable useHoldOutMatte.
Using the replaceColour Parameter
You can also use the holdout matte with the Keylight replaceColour parameter to help
eliminate the yellowish tint. This is for areas that are keyed out by mistake because
they are lit with more blue light than white light, and are also included in the holdout
matte area.
To help correct the lighting with replaceColour:
1 In the Viewer, show the composite (press C with the pointer in the Viewer).
2 In the Keylight1 parameters, click the replaceColour color control.
3 In the Viewer, select a color that is the opposite of the warm yellow—a mid-saturation
purple.
In the following split illustration, the uncorrected yellowish image is on the left. The
image with the replace color is on the right.
As an end note, like all keyers, Keylight is not a magic bullet—a key rarely works with a
single pixel scrub. Feel free to use Keylight in conjunction with other mask techniques
and keyers, and combine the keys through the use of the KeyMix function, or through
the addition or subtraction of mattes with tools such as the IMult, IAdd, Outside, Inside,
KeyMix, and Max nodes.
Without holdout matte With holdout matte