Apple Shake 4 Tutorials - Manual (Page 181)

Chapter 5 Using Keylight 181
6 Insert a Filter–DilateErode node and a Filter–Blur node between the HoldKey and
Keylight1 nodes.
7 In the DilateErode1 parameters, set xPixels and yPixels to approximately –3 to chew into
the matte.
8 In the Blur1 parameters, set xPixels and yPixels to approximately 6 to soften the matte.
The holdout matte strengthens the normal key pulled by Keylight1. Because the
DilateErode1 node reduces the size of the HoldKey holdout matte, the matte does not
interfere with the edges.
HoldKey matte with dilate and Keylight