Apply the linear color key effect – Adobe After Effects CS4 User Manual
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USING AFTER EFFECTS CS4
Effects and animation presets
Last updated 12/21/2009
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.
More Help topics
Keying introduction and resources
Apply the Linear Color Key effect
In the Effect Controls panel, the Linear Color Key effect displays two thumbnail images; the left thumbnail image represents
the unaltered source image, and the right thumbnail image represents the view you’ve selected in the View menu.
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 may 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.
1
Select a layer as the source layer, and then choose Effect > Keying > Linear Color Key.
2
In the Effect Controls panel, choose Key Colors from the Key Operation menu.
3
Choose a color space from the Match Colors menu. In most cases, use the default RGB setting. If you have trouble
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. To see other results, work in one of the other views:
Source Only
Shows the original image without the key applied.
Matte Only
Shows the alpha channel matte. Use this view to check for holes in the transparency. To fill undesired holes
after you complete the keying process, see “
5
Select a key color in one of the following ways:
•
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 pointer 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 pointer 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 transparent.
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.