Adobe After Effects CS4 - Manual (Page 520)

514 USING AFTER EFFECTS CS4
Effects and animation presets
Last updated 12/21/2009
6 Adjust matching tolerance in one of the following ways:
• Select the Plus (+) or the Minus (-) eyedropper, and then click a color in the left thumbnail image. The Plus
eyedropper adds the specified color to the key color range, increasing the matching tolerance and the level of
transparency. The Minus eyedropper subtracts the specified color from the key color range, decreasing the
matching tolerance and the level of transparency.
• Drag the matching tolerance slider. A value of 0 makes the entire image opaque; a value of 100 makes the entire
image transparent.
7 Drag the Matching Softness slider to soften the matching tolerance by tapering the tolerance value. Typically, values
under 20% produce the best results.
8 Before closing the Effect Controls panel, make sure to select Final Output from the View menu to ensure that After
Effects renders the transparency.
Preserve a color after applying Linear Color Key
1 In the Effect Controls panel or Timeline panel, turn off any current instances of keys or matte effects by deselecting
the Effect option to the left of the key name or tool name. Deselecting the option causes the original image to appear
in the Composition panel so that you can select a color to preserve.
2 Choose Effect > Keying > Linear Color Key. A second set of Linear Color Key controls appears in the Effect
Controls panel below the first set.
3 In the Effect Controls panel, choose Keep Colors from the Key Operation menu.
4 Select the color you want to keep.
5 In the first application of the Linear Color Key effect, choose Final Output from the View menu in the Effect
Controls panel, and then turn other instances of the Linear Color Key effect back on to examine the transparency.
You may need to adjust colors or reapply the key a third time to get the results you need.
Luma Key effect
Note: Though the color keying effects built into After Effects can be useful for some purposes, you should try keying with
Keylight before attempting to use these built-in keying effects. Some keying effects have been superseded by more modern
effects like Keylight.
For information about keying in general, including links to tutorials and other resources, see “ Keying introduction and
resources ” on page 383.
The Luma Key effect keys out all the regions of a layer with a specified luminance or brightness. The quality setting of
the layer doesn’t influence the Luma Key effect.
Use this effect if the object from which you want to create a matte has a greatly different luminance value than its
background. For example, if you want to create a matte for musical notes on a white background, you can key out the
brighter values; the dark musical notes become the only opaque areas.
This effect works with 8-bpc and 16-bpc color.