Classroom in a book

Using matte keys
Matte keys cut “holes” in one clip to allow portions of another to show through or 
to create something like cutout figures you can place on top of other clips.
The nomenclature can be confusing. Matte keys are not the same as color mattes, 
such as the brown matte you used earlier in this lesson. However, matte keys 
generally use matte graphics that you create to define the areas you want to make 
transparent or opaque.

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LESSON 15 Exploring Compositing Techniques
Two basic types of matte keys exist:
t
Garbage
: Garbage mattes are four-, eight-, or sixteen-sided polygons. They’re 
named 
garbage
because you typically use them to remove something you don’t 
want in the video. You move their vertices to define the outline of an area you 
want to display.
t
Graphic
: Graphic mattes are shapes that you create for keying out or keying in 
another graphic or a clip. Types of graphic mattes include Difference Matte Key, 
Image Matte Key, Remove Matte Key, and Track Matte Key.
In this exercise, you’ll work with the Four-Point Garbage Matte Key effect and the 
Track Matte Key effect.
1
Load Lesson 15-4.prproj.
2
Drag the Medieval.psd clip to Video 3, and stretch it to be the same length as 
the video clip.
Your goal is to cut out a box around the hero’s face and make it an overlay on 
the upper right of the video.
3
Drag the Four-Point Garbage Matte Key effect from the Keying folder to the 
Medieval.psd clip.

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ADOBE PREMIERE PRO CS5 CLASSROOM IN A BOOK
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4
Click the Medieval.psd clip in the Timeline to select it; then open the Effect 
Controls panel and click the Four-Point Garbage Matte title. This will activate 
the four control points in the garbage matte. Use your mouse to drag the four 
control points in the Program Monitor to create a box around the hero’s face in 
the image. Zoom the Program Monitor to make finer adjustments.