Holdout masks – Apple Motion 5.1.1 User Manual
Page 511
Chapter 13
Keying
511
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 clothing 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, small parts
of the bird’s head and wings are getting removed with the key, rather than just the blue sky. If
left uncorrected, the background image would show through the bird in these areas.
Keyed image with “dirt” on the key
Original image
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. For more information on the Spill Suppressor
filter, see
on page 509.
Create a holdout mask
1
Key the foreground subject.
For more information about using Motion’s keyer filter, see
on page 488.
2
Duplicate the keyed layer.
3
On the newly duplicated layer (above the original layer in the Layers list or Timeline), delete the
original keying filters.
If you’ve used a Spill Suppressor filter, don’t delete it, because it’s probably changing the color of
the subject.
4
On the newly duplicated layer, mask the area of the foreground that is incorrectly keyed.
Make sure that the mask is entirely within the subject being keyed.
Note: The holdout mask must be animated if the subject is moving.
5
If necessary, feather the edge of the mask you’ve just created, to make sure that it blends in with
the object you initially keyed.
67% resize factor