Apple Motion 2 - Manual (Page 870)

870 Chapter 12 Using Shapes and Masks
Garbage Masks
The second step in most keying shots is to create a garbage mask to crop out
unwanted objects in the shot that can’t be keyed, such as the edge of a bluescreen
stage, lighting rigs, or tape that appears in the background.
You can also use a garbage matte to mask out parts of the background that are too
difficult to key without the loss of foreground detail.
To create a garbage mask:
m Select a keyed object, and use one of the mask tools to draw a mask around the
foreground subject.
Note: You may need to animate the garbage mask if the subject is moving.
By default, the mask is set to Add, and crops out everything outside the mask, while
leaving the transparent areas within the mask alone.
For more information about using Motion’s keying filters, see “ Keying Filters ” on
page 760.
01112.book Page 870 Sunday, March 13, 2005 10:36 PM