5.1.1

Chapter 13 Keying 493
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Chroma: Drag the two graphs in this color wheel control to adjust the isolated range of hue
and saturation that help dene the keyed matte. The selected mode governs which graphs
in the color wheel are adjustable. The outer graph controls the softness (edge transparency)
of the matte you’re creating, and can be adjusted in either Scrub Boxes or Manual mode.
The inner graph controls tolerance (core transparency), and is only adjustable when in
Manual mode.
Drag any side of either graph to expand or contract the graph’s border, which adds to or
subtracts from the range of hue and saturation contributing to the key. In manual mode, you
can also drag inside the tolerance graph to adjust its overall position in the color wheel.
To the left of the color wheel, a small graph displays the slope of chroma rollo, the relative
softness of matte edges in regions most aected by the Chroma control. Dragging the Chroma
Rollo slider (described below) modies the shape of this slope.
It’s possible to zoom into and pan around the Chroma control to more precisely adjust the graphs:
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Zooming the Chroma control: To zoom incrementally into the Chroma control, hold down the
Z key and click the color wheel. To zoom out, hold down the Option and Z keys and click the
color wheel. To smoothly zoom out, hold down the Z key and drag left in the color wheel. To
smoothly zoom in, hold down the Z key and drag right in the color wheel. You can also hold
down the Space bar and Command key (in that order), and drag left in the color wheel to
zoom out or drag right to zoom in.
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Panning the Chroma control: To pan in the Chroma control, hold down the H key and drag in
the color wheel. You can also hold down the Space bar and drag in the color wheel in the
direction you want to move it.
To reset the zoom and recenter the Chroma control, move the pointer over the Chroma
control and press Shift-Z.
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Luma: Drag the adjustable handles in this grayscale gradient to modify the isolated range
of the luma channel (the range of lightness and darkness) that also helps dene the keyed
matte. The upper handles (which only appear in Manual mode) adjust the tolerance (core
transparency) of the luma channel’s contribution to the key. The lower handles adjust the
softness (edge transparency) of the luma channel’s contribution to the key.
The Graph mode governs which handles are adjustable. In Scrub Boxes mode, you can adjust
only the lower softness handles, which modify the range of lightness and darkness aecting
the edge transparency the matte. In addition to using the handles, you can drag the slope in
the graph to adjust the softness.
In Manual mode, you can also adjust the upper tolerance handles, which modify core
transparency within the luma channel of the matte. Dragging the slope in the graph adjusts
the lower handles (the softness). To adjust all handles simultaneously, drag inside the curve in
the graph.
By default, the slope of the left and right sides of the Luma graph has a slight “S” curve. You
can modify the shape of the curve by adjusting the Luma Rollo slider (described below).
Note: The luma softness handles may extend past the outer boundaries of the Luma control.
This is due to the oating-point precision of the Keyer lter, and is an expected behavior.
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Chroma Rollo: Use this slider to adjust the linearity of the chroma rollo slope (displayed in the
small graph to the left of the Chroma control). Chroma rollo modies the softness of the matte
around the edges of regions that are aected most by the Chroma control. Lowering this value
makes the slope of the graph more linear, which softens the edges of the matte. Raising this
value makes the slope of the graph steeper, which sharpens the edges of the matte.
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