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603Final Cut Pro User Guide
5. To adjust the softness of the edges, adjust the Luma Rolloff control.
Higher values make the edges harder, removing any partial transparency; lower values
take advantage of any anti-aliasing or softness the edges might have.
6. To help fine-tune the key, use the View options:
• Composite: Shows the final composited image, with the keyed foreground subject
over the background clip. This is the default view.
• Matte: Shows the grayscale matte, or alpha channel, that’s being generated by the
keying operation. White areas are solid, black areas are transparent, and shades
of gray indicate varying levels of transparency. Viewing the alpha channel makes it
easier to spot unwanted holes in the key or areas that aren’t transparent enough.
• Original: Shows the original, unkeyed image.
7. To leave smoothly aliased text or graphics in the image visually intact, which can
improve the edges, select Preserve RGB.
8. To mix the keyed effect with the unkeyed effect, adjust the Mix control.
If you’re still having trouble getting a clean luma key, see the following instructions.
Make advanced luma key adjustments
The following controls are available for use in difficult keying situations or for fine-tuning
specific problems:
• Matte Tools: These controls refine the transparency matte generated by the previous
sets of parameters. These parameters don’t alter the range of values sampled to create
the keyed matte. Instead, they alter the matte generated by the Keyer effect’s basic and
advanced controls, letting you shrink, expand, soften, or invert the matte to achieve a
better composite.
• Light Wrap: These controls blend color and lightness values from the background
layer of your composite with the keyed foreground layer. Using these controls, you can
simulate the interaction of environmental lighting with the keyed subject, making it
appear as if background light wraps around the edges of a subject.