Apple Motion 5.1.1 - Manual (Page 489)

Chapter 13 Keying 489
Refine Key tools
Use the Refine Key tools to manually sample regions of an image to modify the tolerance, or
core transparency, of the generated key. You can sample multiple regions in an image or in a
single frame of a movie clip. You can also sample regions across multiple frames of a clip or
image sequence to compensate for changing conditions, such as shifting lighting that affects the
keyed background.
When you sample regions in multiple frames, keyframes are added to interpolate the difference
from one frame to the next. (Unlike standard keyframes, color-sampling keyframes are hidden in
the Motion workspace by default.) The Jump to Sample buttons let you navigate between frames
you’ve sampled, to make changes. For more information on keyframing the Keyer filter, see
Animate parameters in the Keyer filter on page 504.
There are two Refine Key tools:
•
Sample Color: Use this tool to select regions of the image to be turned transparent. Click the
Sample Color tool, then drag a selection box in the Canvas to define a range of color to key.
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.
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