Adobe Premiere Pro CS6 - Manual (Page 417)

Image Matte Key effect
The Image Matte Key effect keys out areas of a clip’s image based on the luminance values of a still image clip, which serves as a matte. The
transparent areas reveal the image produced by clips in lower tracks. You can specify any still image clip in the project to serve as the matte; it
does not have to be in the sequence. To use a moving image as the matte, use the Track Matte Key effect instead.
Define transparent areas with Image Matte Key
The Image Matte Key determines transparent areas based on a matte image’s alpha channel or brightness values. To get the most predictable
results, choose a grayscale image for your image matte, unless you want to alter colors in the clip. Any color in the image matte removes the
same level of color from the clip you are keying. For example, white areas in the clip that correspond to red areas in the image matte appear blue-
green (since white in an RGB image is composed of 100% red, 100% blue, and 100% green); because red also becomes transparent in the clip,
only blue and green colors remain at their original values.
Note: You can use the Titler to create shapes and text to use as mattes.
A still image used as a matte (left) defines transparent areas in the superimposed clip (center), revealing background clip (right).
1. Add the clip (used as a background) to a video track in a Timeline panel.
2. Add the clip you want to superimpose to any track higher than the track containing the background clip. This is the clip revealed by the track
matte.
Be sure the superimposed clip overlaps the background clip in a Timeline panel.
3. In the Effects panel, click the triangle to expand the Video Effects bin and then click the triangle to expand the Keying bin.
4. Drag the Image Matte Key to the superimposed clip in a Timeline panel.
5. In a Timeline panel, select the superimposed clip.
6. In the Effect Controls panel, click the triangle to expand the Image Matte Key settings.
7. Click the Setup button , browse to the image being used as the matte, and then click Open to select the image.
8. (Optional) If you’re animating the Image Matte Key over time, make sure that the current-time indicator is in the position you want. Click the
Toggle Animation icons for the settings you adjust.
9. Click the Composite Using menu and choose one of the following:
Matte Alpha Composites the clips using the alpha channel values of the image matte you selected in step 7.
Matte Luma Composites the clips using the luminance values of the image matte you selected in step 7.
10. (Optional) Select the Reverse option to swap the areas that are opaque and transparent.
11. (Optional) If you’re animating the Image Matte Key, move the current-time indicator either in the Effect Controls panel or Timeline panel and
change the Image Matte Key settings.
A new keyframe appears in the Effect Controls timeline when you change the settings. Repeat this step as needed. You can also adjust the
interpolation between keyframes by editing the keyframe graph.
Luma Key effect
The Luma Key effect keys out all the regions of a layer with a specified luminance or brightness.
Use this effect if the object from which you want to create a matte has a greatly different luminance value than its background. For example, if you
want to create a matte for musical notes on a white background, you can key out the brighter values; the dark musical notes become the only
opaque areas.
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