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Chapter 12 Keyingandcompositing 391
 Luma Rollo: Use this slider to adjust the linearity of the luma rollo slope (the ends
of the bell-shaped luma curve displayed in the Luma control). Luma rollo modies
the softness of the matte around the edges of regions that are aected most by the
Luma control. Lowering this value makes the slope between the upper and lower
handles in the Luma control more linear, which increases edge softness in the matte.
Raising this value makes the slope steeper, sharpening the edges of the matte and
making them more abrupt.
 Fix Video: Select this checkbox to apply subpixel smoothing to the chroma
components of the image, reducing the jagged edges that result from keying
compressed media using 4:2:0, 4:1:1, or 4:2:2 chroma subsampling. Although
selected by default, this checkbox can be deselected if subpixel smoothing
degrades the quality of your keys.
3 Click Matte Tools to reveal the following controls:
 Levels: Use this grayscale gradient to alter the contrast of the keyed matte, by
dragging three handles that set the black point, white point, and bias (distribution
of gray values between the black point and white point). Adjusting the contrast of
a matte can be useful for manipulating translucent areas of the key to make them
more solid (by lowering the white point) or more translucent (by raising the black
point). Dragging the Bias handle right erodes translucent regions of the key, while
dragging the Bias handle left makes translucent regions of the key more solid.
 Black, White, Bias: Click the disclosure triangle in the Levels row to reveal sliders for
the Black, White, and Bias parameters. These sliders, which mirror the settings of the
Levels handles described above, allow you to keyframe the three Levels parameters
(via the Add Keyframe button to the right of each slider). Keyframing the Black,
White, and Bias parameters may yield a better key, one that adapts to changing
blue-screen or green-screen conditions.
 Shrink/Expand: Use this slider to manipulate the contrast of the matte to aect matte
translucence and matte size simultaneously. Drag the slider left to make translucent
regions more translucent while simultaneously shrinking the matte. Drag the slider
right to make translucent regions more solid while simultaneously expanding
the matte.