ADOBE AFTER EFFECTS 7.0
User Guide
463
Paint Style Specifies whether the stroke is applied to the original layer or to a transparent layer.
Keying effects
Color Difference Key effect (Pro only)
The Color Difference Key effect creates transparency from opposite starting points by dividing an image into two
mattes, Matte Partial A and Matte Partial B. Matte Partial B bases the transparency on the specified key color, and
Matte Partial A bases transparency on areas of the image that do not contain a second, different color. By combining
the two mattes into a third matte, called the alpha matte, the Color Difference Key creates well-defined trans-
parency values.
The Color Difference Key produces high-quality keying for all well-lit footage items shot against a bluescreen or
greenscreen and works especially well with images that contain transparent or semitransparent areas, such as smoke,
shadows, or glass.
This effect works with 8-bpc and 16-bpc color.
Original (left) and background layer (center) are combined using Color Difference Key (right).
See also
“To use the Color Difference Key effect” on page 273
Color Key effect
The Color Key effect keys out all image pixels that are similar to a specified key color. This effect modifies only the
alpha channel of a layer. The layer’s quality setting does not affect Color Key.
This effect works with 8-bpc and 16-bpc color.
A non-standard color screen (left) and the background (center) are combined with Color Key (right).
When you key out a color value in a layer, that color or range of colors becomes transparent for the entire layer.
Control the range of transparent colors by adjusting the tolerance level. You can also feather the edges of the trans-
parent area to create a smooth transition between the transparent and opaque areas.
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