Apple Color 1.5 - Manual (Page 300)

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 node
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.
When you’re finished with the effect, you need to reassemble the fields into frames using
the Interlace node, connecting the Even branch of the node tree to the Even input on
the left and the Odd branch of the node tree to the Odd input on the right. The Output
node is attached to the Interlace node, and you’re finished.
300 Chapter 11 The Color FX Room