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See also
"To set background or pasteboard color" on page 117
"To create a solid-color layer" on page 150
Recommendations for sequencing and combining keys
When creating transparency in footage, you may need to try different keys before you are satisfied with the results.
You can also combine two or more keys or Matte effects. Because keys are treated as effects, you can easily turn them
on or off by clicking the Effect switch to the left of the effect name in the Effect Controls panel or in the Timeline
panel. Use the following recommendations for combining keys for specific types of footage items:
•
To create transparency in well-lit footage shot against a bluescreen or greenscreen, start with the Color Difference
Key. Add the Spill Suppressor to remove traces of the key color, and then use one or more of the other Matte effects,
if necessary. If you are not satisfied with the results, try starting again with the Linear Color Key.
•
To create transparency in footage shot against multiple colors or to create transparency in unevenly lit footage shot
against a bluescreen or greenscreen, start with the Color Range key. Add the Spill Suppressor and other effects to
refine the matte. If you are not completely satisfied with the results, try starting with or adding the Linear Color
Key.
•
To create transparency in dark areas or shadows, use the Extract Key on the Luminance channel.
•
To make a static background scene transparent, use the Difference Matte Key. Add the Simple Choker and other
effects as needed to refine the matte.
See also
"Matte Choker effect (Pro only)" on page 466
"Simple Choker effect (Pro only)" on page 467
About binary keys
The simplest type of key is the binary key, which creates pixels that are either entirely transparent or entirely opaque.
Pixels that match the specified key color are made transparent; those that don't match remain opaque. Because binary
keys do not create semitransparent pixels, they are best for solid objects with sharp, defined edges, such as titles or
credits, or for footage items with a solid color background and no changes in background lighting.
Using the Linear Color Key effect
Linear keys create a range of transparency across an image. A linear key compares each pixel in the image to the key
color you specify. If the color of a pixel closely matches the key color, it becomes completely transparent. Pixels that
don't match as well are made less transparent, and pixels that don't match at all remain opaque. The range of trans-
parency values, therefore, forms a linear progression.
To apply the Linear Color Key effect
In the Effect Controls panel, the Linear Color Key effect displays two thumbnail images; the left thumbnail image
represents the unaltered source image, and the right thumbnail image represents the view you've selected in the View
menu.
You can adjust the key color, the matching tolerance, and the matching softness. The matching tolerance specifies
how closely pixels must match the key color before they start becoming transparent. The matching softness controls
the softness of edges between the image and the key color.
ADOBE AFTER EFFECTS 7.0
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