5

After you create a selection box, you can resize it to sample more or fewer shades of
color, increasing or decreasing the range of background color used to create
transparency. You can also add more selection boxes to expand the range of color that
is keyed. You can also add more sample color boxes at other frames of the clip to
maintain transparency when lighting conditions change.
To add selection boxes, select the Keyer filter in the Layers list, then hold down the
Shift key while dragging in the Canvas.
Note: Adding a Sample Color selection box to a frame adds to the sampled region
that’s defined when you first apply this filter.
• Edges: Use this tool to refine the transparency of marginal regions of the keyed subject,
such as hair, reflections, smoke, or moving subjects with motion blur. Click the Edges
tool, then drag in the Canvas to draw a line that crosses the boundary of the
semitransparent region you want to adjust (with one point on the keyed foreground
subject and the other point on the transparent background). Next, adjust the slider
handle in the middle of this control line, outward to soften the matte, or inward to
harden it.
If the Keyer filter is selected in the Layers list, you can press the Command key and drag
in the Canvas to create Edges sampling controls.
640 Chapter 13 Keying