Apple Color 1.0 - Manual (Page 247)

Chapter 11 Color FX 247
This matte is connected to the Alpha input of the Alpha Blend node (the third input). A
blur node is then connected to the Source 2 input.
The Blur node blurs the corrected image, but the matte image that’s connected to the
alpha input limits its effect to the areas of the image that don’t include the image detail
around the edges that were isolated using the Edge Detector node.
As you can see, the image that’s connected to the Alpha input of the Alpha Blend
mode limits the way the Source 1 and Source 2 inputs are combined. This is but one
example of the power of the Alpha Blend node. You can use this node to limit many
different effects.
Using Color FX with Interlaced Shots
One of the limitations of the Color FX room is that many effects need to be specially
assembled when you’re working on interlaced video.
When you’re creating an effect for an interlaced shot, you need to separate each field at
the beginning of the node tree with two Deinterlace nodes, one set to Even and one
set to Odd. Once that’s done, you need to process each individual field using identical
node trees.