Adobe 12040118 - After Effects Standard Tutorial page 440

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 Close a hole in a matte.
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.
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
For information about keying in general, including links to tutorials and other resources, see Keying introduction and resources.
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.
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