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Chapter 12 Keyingandcompositing 397
4 To adjust the white and black clip values, drag the handles at either end of the
gradient thumbnail image.
By default, these handles are set to provide a linear key where the luma level linearly
controls the transparency of the foreground—100% white is fully opaque, 0% black is
completely transparent, and 25% gray retains 25% of the foreground image. Dragging
the white and black controls changes the values that result in fully opaque or fully
transparent foreground video.
5 To adjust the softness of the edges, adjust the Luma Rollo control.
Higher values make the edges harder, removing any partial transparency, while lower
values take advantage of any anti-aliasing or softness the edges might have.
6 To help ne-tune the key, use the View options:
Original
(unprocessed
foreground)
Matte (foreground-based
alpha signal created
by the keyer)
Composite
(foreground combined
with background)
The name of the
currently selected
View button
 Composite: Shows the nal 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
varying 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 eect with the unkeyed eect, adjust the Mix control.
For information about making advanced luma key adjustments, see the following
instructions.