Holdout masks – Apple Motion 3 User Manual
Page 1110
1110
Chapter 12
Using Shapes and Masks
Holdout Masks
Sometimes, while pulling a key, you lose part of the image you’re trying to keep. This
can happen when the color of the subject’s clothes is too close to the color of the
background being keyed out, or when you need to use keying values that are too
aggressive. In this example, very small parts of the lioness’s head and face are getting
removed with the key, rather than just the blue sky.
In these cases, you can duplicate the original layer, mask the part of the subject that’s
being incorrectly keyed, and composite it over the keyed version to fill it back in.
Note: The Spill Suppressor filter can modify the color of the foreground subject as well.
If you’re using the Spill Suppressor filter on the keyed layer, you may have to apply the
same filter to the holdout mask layer to make sure the color matches.
To create a holdout mask:
1
Key and mask the foreground subject.
For more information about using Motion’s keying filters, see “
2
Duplicate the keyed layer, then move it so that it appears above the original layer in the
Layers tab or Timeline layers list.
3
Mask the area of the foreground that is incorrectly keyed.
Original image of lion
The lion image key leaves black spots or “dirt”
on the key. The background image would show
through the lion in these areas.