Apple Motion 3 User Manual
Page 1111

Chapter 12
Using Shapes and Masks
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Make sure that the mask is entirely within the subject being keyed.
Note: You may need to animate the holdout mask if the subject is moving.
4
On the newly duplicated layer, delete the original keying filters since they’re
unnecessary.
If you’ve used a Spill Suppressor filter, don’t delete it, since it’s probably changing the
color of the subject.
5
Feather the edge of the holdout mask you’ve just created, to make sure that it blends
in with the object you initially keyed.
6
As an optional step, you can nest the originally keyed layer along with the holdout
matte you just created inside a dedicated group so that you can manipulate the entire
subject as a single object.
Final composite
The mask on the lioness’s head creates a clean
key by removing the “dirt” left by the original
key.