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Using Help | Contents | Index Back 231
Adobe Premiere Pro Help Superimposing and Compositing
Using Help | Contents | Index Back 231
In this way, you can replace a static background behind a moving object (such as a person
walking past a stage set). Very often the specified image is simply a frame of background
footage (before the moving object enters the scene). For this reason, the Difference Matte
key is best used for scenes that have been shot with a stationary camera.
To replace a static background behind a moving object:
1 Find a frame of your clip that consists only of the static background.
2 Save this frame as an image file. (For information about saving a frame, see “Exporting a
still image” on page 300.)
3 Place the video clip in a track.
4 In the Effects window, expand the Video Effects bin and then the Keying bin.
5 Drag the Difference Matte effect to the video clip.
6 Click Setup to select the frame you saved.
7 Select the Reverse Key option to key out the static background.
8 Adjust options as needed.
Setup Click to select an image to use as the difference matte.
Similarity Broadens or reduces the range of color that will be made transparent. Higher
values
increase the range.
Smoothing Specifies the amount of anti-aliasing (softening) that Adobe Premiere Pro
applies to the boundary between transparent and opaque regions. Choose None to
produce sharp edges, with
no anti-aliasing. This option is useful when you want to
preserve sharp lines, such as those in
titles. Choose Low or High to produce different
amounts of smoothing.
Reverse Inverts the values of the matte.
Drop Shadow Adds a 50% gray, 50% opaque shadow offset from the opaque areas of the
original clip image by four pixels down and to the right. This option works best with
simple graphics such as titles.
Mask Only Displays only the clip’s alpha channel, as modified by the key settings.
Using the Track Matte key
Use the Track Matte key to show one clip through another, using a third file as a matte that
creates transparent areas in the superimposed clip. This effect requires two clips and a
matte, each placed on its own track. You may want to set aside an entire track for the
matte, because you must hide that track. White areas in the matte are opaque in the
superimposed clip, preventing underlying clips from showing through. Black areas in the
matte are transparent, and gray areas are partially transparent.