Extract effect – Adobe After Effects CS4 User Manual
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USING AFTER EFFECTS CS4
Effects and animation presets
Last updated 12/21/2009
Note: If the shot doesn’t contain a full background frame, you may be able to assemble the full background by combining
parts of several frames in After Effects or Photoshop. For example, you can use the Clone Stamp tool to take a sample of
the background in one frame, and then paint the sample over part of the background in another frame.
4
Turn off the display of the difference layer by clicking the Video switch in the Timeline panel.
5
Make sure that the original source layer is selected, and then choose Effect > Keying > Difference Matte.
6
In the Effect Controls panel, choose Final Output or Matte Only from the View menu. (Use the Matte Only view
to check for holes in the transparency. To fill undesired holes after you complete the keying process, see “
7
Select the background file from the Difference Layer menu.
8
If the difference layer isn’t the same size as the source layer, choose one of the following controls from the If Layer
Sizes Differ menu:
Center
Places the difference layer in the center of the source layer. If the difference layer is smaller than the source
layer, the rest of the layer fills with black.
Stretch To Fit
Stretches or shrinks the difference layer to the size of the source layer. Background images may become
distorted.
9
Adjust the Matching Tolerance slider to specify the amount of transparency based on how closely colors must
match between the layers. Lower values produce less transparency; higher values produce more transparency.
10
Adjust the Matching Softness slider to soften the edges between transparent and opaque areas. Higher values make
matched pixels more transparent but don’t increase the number of matching pixels.
11
If the matte still contains extraneous pixels, adjust the Blur Before Difference slider. This slider suppresses noise by
slightly blurring both layers before the comparison is made.
Note: The blurring occurs only for the comparison and doesn’t blur final output.
12
Before closing the Effect Controls panel, make sure to select Final Output from the View menu to ensure that After
Effects renders the transparency.
Extract effect
The Extract effect creates transparency by keying out a specified brightness range, based on a histogram of a specified
channel. It’s best used to create transparency in an image shot against a black or white background or against a
background that is dark or bright but consists of more than one color.
Note: The controls for this effect are similar to the controls of the Extract effect in Adobe Premiere Pro, but the purpose
and results of the effect are different.
This effect works with 8-bpc and 16-bpc color.
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