Adobe AFTER EFFECTS CS3 PROFESSIONAL User Manual page 450

Note: Make sure that the mask mode for all masks is set to None.
2 If you want, move the masks around to find the location that provides the best results.
To extract more than one object, or to create a hole in an object, draw additional masks and then select them from
3
the Additional Foreground and Additional Background menus. For example, to key out a woman's hair blowing in
the wind against a blue sky, draw the inner mask inside her head, draw the outer mask around the outside edge of
her hair, and then draw an additional mask around the gap in her hair where you can see sky. Select the additional
mask from the Additional Foreground menu to extract the gap and remove the background image.
Create additional open or closed masks to clean up other areas of the image, and then select them from the
4
Cleanup Foreground or Cleanup Background menu. Cleanup Foreground masks increase the opacity along the
mask; Cleanup Background masks decrease the opacity along the mask. Use the Brush Radius and Brush Pressure
options to control the size and density of each stroke.
Note: You can select the Background (outer) mask as a Cleanup Background mask to clean up noise from the
background portions of the image.
Set Edge Thin to specify how much of the matte's border is affected by the key. A positive value moves the edge
5
away from the transparent region, increasing the transparent area; a negative value moves the edge toward the trans-
parent region and increases the size of the foreground area.
6 Increase the Edge Feather values to soften edges of the keyed area. High Edge Feather values take longer to render.
Specify the Edge Threshold, which is a soft cutoff for removing low-opacity pixels that can cause unwanted noise
7
in the image background.
Select Invert Extraction to reverse the foreground and background regions.
8
Set Blend With Original to specify the degree to which the resulting extracted image blends with the original
9
image.
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.
The Linear Color Key effect uses RGB, hue, or chroma information to create transparency from a specified key color.
This effect works with 8-bpc, 16-bpc, and 32-bpc color.
See also
"Keying overview" on page 268
"Matte Choker effect" on page 448
"Simple Choker effect" on page 448
Apply the Linear Color Key effect
In the Effect Controls panel, the Linear Color Key effect displays two thumbnail images; the left thumbnail image repre-
sents the unaltered source image, and the right thumbnail image represents the view you've selected in the View menu.
AFTER EFFECTS CS3 444
User Guide