Adobe After Effects CS3 - Manual (Page 391)

AFTER EFFECTS CS3
User Guide
386
Use Background Color to specify the new background color. To allow this effect to generate color values outside of
the range 0.0-1.0 when working in 32-bpc color, deselect Clip HDR Values.
This effect works with 8-bpc, 16-bpc, and 32-bpc color.
Original (left), and with Remove Color Matting effect applied (right)
Set Channels effect
The Set Channels effect copies channels from control layers (source layers) to the red, green, blue, and alpha channels
of the effect layer. For example, you can take the luminance values of a control layer’s pixels and use them as the blue
values for the effect layer’s pixels.
This effect works with 8-bpc and 16-bpc color.
Set Matte effect
The Set Matte effect replaces the alpha channel (matte) of a layer with a channel from another layer above it for the
creation of traveling matte results. The Set Matte effect is intended only to provide compatibility with projects created
in earlier versions of After Effects that use the Set Matte effect.
This effect works with 8-bpc and 16-bpc color.
Original (top left), matte layer (bottom left), and result (bottom right)
Although you can use Set Matte for a traveling matte, it’s easier and faster to create traveling mattes by using a track
matte. (See “About track mattes and traveling mattes” on page 263.)
Take Matte From Layer The layer to use as the replacement matte.
Use For Matte The channel to use for the matte.
Invert Matte Inverts the transparency values of the matte.
Stretch Matte To Fit Scales the selected layer to match the size of the current layer. If Stretch Matte To Fit is
deselected, the layer designated as the matte is centered in the first layer.