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596Final Cut Pro User Guide
• Graph: Provides two options to set how the adjustable graphs in the Chroma and
Luma controls are used to fine-tune a key:
• Scrub Boxes: Select to limit the Chroma and Luma controls to adjusting softness
(edge transparency) in the matte you’re creating. In this mode, you can’t
manually adjust tolerance (core transparency), which is determined by the Keyer
effect’s automatic sampling, plus any Sample Color rectangles you’ve added in
the viewer. (To increase matte tolerance, add more Sample Color rectangles or
adjust the Strength slider.)
• Manual: Select to use the Chroma and Luma controls to adjust the softness (edge
transparency) and tolerance (core transparency) in the matte you’re creating.
Make sure the Strength slider is set to a value greater than 0% before you switch
to Manual mode; otherwise the Chroma and Luma controls are disabled. When
you switch to Manual mode, the Refine Key tools and Strength slider become
disabled, but samples you’ve made with those controls continue to contribute to
the matte.
Important: When you switch to Manual mode, it’s best not to switch back to Scrub
Boxes mode. For best results, begin keying an image using the Sample Color and
Edges tools in Scrub Boxes mode. Switch to Manual mode afterward if you feel it’s
necessary to refine your matte using the Chroma and Luma controls. However, if you
switch back to Scrub Boxes mode, you may experience unexpected combinations of
additionally sampled and keyframed values that might be difficult to control.
• Chroma: Drag the two graphs in this color wheel control to adjust the isolated
range of hue and saturation that help define 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 rolloff, the
relative softness of matte edges in regions most affected by the Chroma control.
Dragging the Chroma Rolloff slider (described below) modifies the shape of this
slope.
Tip: It’s possible to zoom in to and pan around the Chroma control to more
precisely adjust the graphs. To zoom in to the Chroma control, move the pointer over
the color wheel and, holding down the Z key, drag to the left to zoom out or to the
right to zoom in. To pan in the Chroma control, hold down the H key 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.