Apple Final Cut Pro 5 - Manual (Page 1172)

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Keying, Mattes, and Masks
You can isolate specific elements of clips from the
background and combine those elements with other
clips by using keying, mattes, and masks.
This chapter covers the following:
 Ways to Layer and Isolate Elements in Clips (p. 385)
 Using Keying to Isolate Foreground Elements (p. 388)
 Using Mattes to Add or Modify Alpha Channels (p. 404)
 Using Masks to Replace or Modify Alpha Channels (p. 407)
Ways to Layer and Isolate Elements in Clips
People have been layering visual elements together since the dawn of the movie
industry. Although digital techniques have increased the potential number of layers
from two or three to two or three thousand (and even more), the same basic principles
are used. The names vary from one industry to the next, but as film and video merge
on a single digital horizon, the terms are becoming more interchangeable.
What Are Mattes and How Can You Use Them?
Matte, or hold matte, originated with film and photography. It traditionally refers to any
opaque material that, when held in front of a camera lens, prevents certain areas of the
film from being exposed during shooting. Then, the camera can be rewound, and a
matte of the opposite shape can be used to prevent exposure on the already exposed
part of the film while the other portion is exposed. The result is two different images
shot at different times combined together in one frame.
The same principle can be used in digital applications. In the case of cameras, the
mattes are hand-made, physical objects, but on a computer they can be drawn and
applied digitally.