Apple Motion 5.1.1 - Manual (Page 487)

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Keying overview
Keying is the process of isolating a foreground subject against a background area of uniform
color or brightness to generate an alpha channel (a matte) based on the shape of the colored
area. Keying is commonly performed on subjects photographed against a blue- or green-
colored background, but keys can be based on any color (color keying), or on a specific range of
brightness values (luma keying).
Color keying (also known as chroma keying) is commonly used on television to create the familiar
effect of a newsreader or show host backed by a cavalcade of animated graphics. You can do the
same thing in Motion using the Keyer filters.
Green screen clip Keyed clip
Important: Keying to isolate a foreground subject is not always easy; learning how to use the
parameters in each filter to best effect takes time and patience. Most keys are “pulled” using more
than one tool. Good compositing artists usually combine masked keyer filters, matte adjustment
filters, spill suppression operations, and garbage or holdout masks to isolate a single subject.
The Keyer filter in Motion combines many of these operations within a single set of parameters.
In some instances, it may be necessary to apply different keyer settings to different areas of the
subject, requiring the use of multiple keying filters and masks.
Keying is accomplished using one of two keyer filters in Motion:
•
Use the Keyer filter for blue screen or green screen keying, or for keying any range of color
you choose.
•
Use the Luma Keyer to generate mattes based on a sampled range of lightness in the image.
Two other Motion keying filters—Matte Magic and Spill Suppression—provide standalone access
to matte finishing operations:
Both keyer filters, as well as the Matte Magic and Spill Suppression filters, are located in the
Keying category of filters in the Motion Library. For more information, see
Manipulate alpha
channels using filters on page 757.
To learn more about keying techniques, choose an item in the Help table of contents (the
sidebar to the left of this window).
Keying
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