5

It’s possible to zoom into and pan around the Chroma control to more precisely adjust
the graphs:
• 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.
• 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.
• 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 define
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
affecting 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 Rolloff slider (described
below).
Note: The luma softness handles may extend past the outer boundaries of the Luma
control. This is due to the floating-point precision of the Keyer filter, and is an expected
behavior.
• Chroma Rolloff: Use this slider to adjust the linearity of the chroma rolloff slope
(displayed in the small graph to the left of the Chroma control). Chroma rolloff modifies
the softness of the matte around the edges of regions that are affected 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.
645Chapter 13 Keying