Visual QuickStart Guide [Electronic resources] : Final Cut Express HD for Mac OS X

Lisa Brenneis

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  • Working with Mattes

    Mattes are filters that you shape to define which areas of opaque video clips are to be made transparent during compositing. For example, you could use a circular matte to isolate a clock face from its background, or you could create a matte in the shape of a keyhole to simulate peeking through a keyhole in a door.

    Final Cut Express offers many types of matte filters (Figure 16.17 ). "Garbage mattes" are used to quickly rough out large areas of the frame. A

    key is a type of matte that uses a clip's color or luminance information to determine which opaque areas will be made transparent (bluescreen effects are created with color key mattes set to make blue areas transparent). You can combine layers of different types of mattes to create very complex composite shapes.

    Figure 16.17. Final Cut Express offers a toolbox full of special-purpose matte and key filters. When you create multilayer compositions, use these filters to mask out portions of the frame.

    To apply a matte:

    1.

    Do one of the following:

    • Drag the Key or Matte filter from the Browser's Effects tab and drop it on the clip in the Timeline.

    • Select the clip in the Timeline and choose Effects > Video Filters; then select a filter from the Key or Matte submenu.

    2.

    Position the playhead over a frame in the selected clip to see a preview of the effect in the Canvas.

    Travel mattes

    A travel matte allows one video clip to play through another. The alpha information in a third clip is used as a matte that defines the transparent and opaque areas of the composited image.

    When you create a travel matte effect, there are usually three video tracks involved; this is sometimes called a "matte sandwich." The background clip is placed on V1, or the lowest video track available. The matte clip, preferably a high-contrast, grayscale motion clip or still image, goes on the video track just above the background clip, on V2; and the foreground clip sits on V3, or the video track above the matte clip. A Composite mode specifically for creating travel mattes, called Travel Matte - Luma, is applied to the foreground clip. If the matte clip is placed on video track V1 without a background clip, then the background is automatically black.

    To create a travel matte:

    1.

    In the Timeline, drag your background clip (Figure 16.18 ) to V1.

    Figure 16.18. Drag your background clip to track V1.

    2.

    Drag the clip selected to be the matte clip (Figure 16.19 ) to V2.

    Figure 16.19. Drag your matte clip to track V2. The white areas in this clip will define the opaque areas of the foreground clip.

    3.

    Drag your foreground clip (Figure 16.20 ) to V3.

    Figure 16.20. Place your foreground clip on track V3.

    4.

    To establish the travel matte, select the foreground clip on V3 (Figure 16.21 ) and choose Modify > Composite Mode > Travel Matte Luma.

    Figure 16.21. To composite the travel matte, select the foreground clip on V3 and choose Modify > Composite Mode > Travel MatteLuma. The foreground clip on V3 is now composited with the matte clip on V2.

    The completed travel matte effect (Figure 16.22 ) uses the matte clip's luminance (or grayscale) levels as the mask. The matte clip's black area creates the shape of the foreground clip's transparent areas, revealing the background clip video. The matte clip's white area creates the shape of the foreground clip's opaque areasthat's where you see the foreground clip's video.

    Figure 16.22. The completed travel matte effect.