5

Luma Rolloff: Use this slider to adjust the linearity of the falloff between the Luma control’s
tolerance and softness handles. Modifying this parameter changes the softness of the
matte around the edges in regions that are affected most by the Luma control. Decreasing
the Luma Rolloff value makes the slope between the two handles of the Luma control
more linear, which visibly increases edge softness. Increasing this value makes the slope
between the handles of the Luma control steeper, sharpening the edges of the matte
and making them more abrupt.
View: Use these buttons to switch among three keying preview modes in the Canvas,
useful for refining your key.
• Composite: When selected, the leftmost button displays the final composited image
in the Canvas, with the keyed foreground subject isolated against a transparent
background, which lets layers underneath show through.
• Matte: When selected, the middle button displays the grayscale matte, or alpha channel,
generated by the keying operation. Viewing the alpha channel lets you evaluate the
parts of the generated matte. Areas in the matte that appear white are visible in the
final composite; areas that appear black are transparent; and areas with shades of gray
are semitransparent (lighter grays being more solid, and darker grays being more
translucent). Viewing the alpha channel makes it easier to spot unwanted holes in the
key, or areas of the key that aren’t transparent enough.
• Original: When selected, the rightmost button displays the original, unkeyed image in
the Canvas.
Matte Tools: Click the disclosure triangle in the Matte Tools row to reveal controls for
post-processing the transparency matte generated by the previous sets of parameters.
These parameters do not alter the range of values sampled to create the keyed matte.
Instead, they alter the matte generated by the Luma and Luma Rolloff controls, letting
you shrink, expand, soften, or invert the matte to achieve a better composite.
• Fill Holes: Use this slider to adjust solidity in regions of marginal transparency throughout
a key. This parameter is useful when you’re satisfied with the edges of your keyed matte
but have unwanted holes in the interior of the foreground subject that you can’t
eliminate using the Strength parameter without ruining edges. Higher slider values fill
more holes in the solid areas of the keyed subject.
661Chapter 13 Keying