Adobe AFTER EFFECTS CS3 PROFESSIONAL User Manual page 451

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.
You can also reapply this key to preserve a color that was made transparent by the first application of the key. For
example, if you key out a medium-blue screen, you might lose some or all of a light-blue piece of clothing your
subject is wearing. You can bring back the light-blue color by applying another instance of the Linear Color Key and
choosing Keep This Color from the Key Operation menu.
Select a layer as the source layer, and then choose Effect > Keying > Linear Color Key.
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2 In the Effect Controls panel, choose Key Colors from the Key Operation menu.
Choose a color space from the Match Colors menu. In most cases, use the default RGB setting. If you have trouble
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isolating the subject using one color space, try using a different color space.
4 In the Effect Controls panel, choose Final Output from the View menu. The view you choose appears in the right
thumbnail and in the Composition panel. If you need to see other results, work in one of the other views:
Shows the original image without the key applied.
Source Only
Shows the alpha channel matte. Use this view to check for holes in the transparency. To fill undesired
Matte Only
holes after you complete the keying process, see "Close a hole in a matte" on page 271.
Select a key color in one of the following ways:
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• Select the Thumbnail eyedropper, and then click an appropriate area in the Composition panel or the original
thumbnail image.
• Select the Key Color eyedropper, and then click an appropriate area in the Composition or Layer panel.
• To preview transparency for different colors, select the Key Color eyedropper, hold down the Alt key (Windows)
or Option key (Mac OS), and move the cursor to different areas in the Composition panel or the original
thumbnail image. The transparency of the image in the Composition panel changes as you move the cursor over
different colors or shades. Click to select the color.
• Click the Key Color swatch to select a color from the specified color space. The selected color becomes trans-
parent.
Note: The eyedropper tools move the sliders accordingly. Use the sliders in steps 6 and 7 to fine-tune the keying results.
To use eyedroppers in the Layer panel, choose Linear Color Key from the View menu in the Layer panel.
Adjust matching tolerance in one of the following ways:
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• 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.
Before closing the Effect Controls panel, make sure to select Final Output from the View menu to ensure that After
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Effects renders the transparency.
AFTER EFFECTS CS3 445
User Guide