Luma key effect – Adobe After Effects CS3 User Manual
Page 453
AFTER EFFECTS CS3
User Guide
448
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 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.
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
The Luma Key effect keys out all the regions of a layer with a specified luminance or brightness. The layer’s quality
setting 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.