Apple Final Cut Pro X (10.1.2) - Manual (Page 354)

354
Keying
Keying overview
There are times when you need to combine two clips to create an image with bits of both. A
common way to combine two clips is to use a keying process, where the video of the top, or
foreground, clip is processed to eliminate either a color or luma value in areas of the video and
then is combined with the bottom, or background, clip.
For example, keying allows you to take a video clip of a person standing in front of a green
background and replace that green with a street scene, making it appear as though that person
is standing on the street.
This type of keying is accomplished using one of two keyer effects in Final Cut Pro:
•
Keyer: This general purpose chroma-keying effect is optimized for blue- or green-screen keying
but can key any range of color you choose. See
Use chroma keys on page 355.
•
Luma Keyer: This is designed to generate mattes based on the image’s lightness—you choose
to remove the white or black areas and whether or not the gray areas should be partially
transparent. See
Use luma keys on page 363.
In addition to these keying effects, you may need to use a matte, a positioning effect, and color
correction to ensure the foreground video looks natural when keyed over the background. For
more information, see
Finalize the key on page 368.
Another way to combine two clips is for the foreground clip to have an alpha or matte
channel that defines which parts of the foreground clip to keep and which to replace with the
background clip. This is common when working with computer-generated logos or animated
graphics. For more information, see
Compositing overview on page 372.
Keying and compositing
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