Keying Effects - Adobe AFTER EFFECTS CS3 PROFESSIONAL User Manual

Keying effects

After Effects includes several built-in keying effects, as well as the Academy Award winning Keylight effect, which
excels at professional-quality color keying. For information on the Keylight effect, see its documentation in this
folder: Adobe After Effects CS3/Additional Documentation/Keylight.
To see a video tutorial on keying with Keylight, visit the Adobe website at www.adobe.com/go/vid0229.
Adobe Creative Suite Production Premium Edition also includes Adobe Ultra, which can quickly key out a poorly
lit background shot with a low-quality webcam.
Color Difference Key effect
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 don't contain a second, different color. By combining
the two mattes into a third matte, called the alpha
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.
See also
"Keying overview" on page 268
"Matte Choker effect" on page 448
"Simple Choker effect" on page 448
Use the Color Difference Key effect
Select the layer you want to make transparent, and then choose Effect > Keying > Color Difference Key.
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Note: To use any of the eyedroppers in the Layer panel, choose Color Difference Key from the View menu in the Layer
panel.
In the Effect Controls panel, choose Matte Corrected from the View menu. To view and compare the source
2
image, both partial mattes, and the final matte at the same time, choose [A, B, Matte] Corrected, Final from the View
menu. Other views available in the View menu are described in step 10.
3 Select the appropriate key color: To key out a bluescreen, use the default blue color. To key out a nonblue screen,
select a key color in one of the following ways:
• Thumbnail eyedropper: Select and then click in the Composition panel or the original thumbnail image on an
appropriate area.
• Key Color eyedropper: Select and then click in the Composition or Layer panel on an appropriate area.
• Key Color swatch: Click to select a color from the specified color space.
Note: The eyedropper tools move the sliders accordingly. Use the sliders in step 9 to fine-tune the keying results.
Click the matte button to display the final combined matte in the matte thumbnail.
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matte, the Color Difference Key creates well-defined trans-
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