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594Final Cut Pro User Guide
4. 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 (the foreground video is opaque), black
areas are transparent (the foreground is not seen at all), and shades of gray indicate
varying levels of transparency (the background video can be seen mixed with the
foreground video). Viewing the matte makes it easier to spot unwanted holes in the
key or areas that aren’t transparent enough.
• Original: Shows the original, unkeyed foreground image.
5. To further refine the matte, use the following controls:
• Fill Holes: Increasing this parameter value adds solidity to regions of marginal
transparency within a key. This control is useful when you’re satisfied with the edges
of your key, but you have unwanted holes in the interior that you can’t eliminate
using the Strength parameter without ruining your edges.
• Edge Distance: Lets you adjust how close to the edge of your keyed subject the
effect of the Fill Holes parameter gets. Reducing this parameter value brings the
filled area of the matte closer to the edge of the subject, sacrificing translucency at
the edges. Increasing this parameter value pushes the filled area of the matte farther
from the edge. Too much edge distance can result in unwanted translucency within
parts of the subject that should be solid.
6. To suppress any of the background color that is appearing (spilling) on the foreground
image, adjust the Spill Level control.
7. To reverse the keying operation, retaining the background color and removing the
foreground image, select Invert.
8. To mix the keyed effect with the unkeyed effect, adjust the Mix control.
If you’re still having trouble getting a clean key, see the following instructions.