This method is an exciting way to focus attention on action. It takes the same basic approach as the previous task, only this time you'll use a track matte. The reason: You want to put that matte in motion.
To accomplish this effect, follow these steps:
Keep your previous project in the timeline. You'll need it in a moment.
Select a clip that has something moving around in it?for instance, a racecar coming out of a turn and down the straightaway, someone walking down a street, or an aerobatic plane doing loops. As with the previous task, place the clip on both Video 1 and Video 2, either ahead of your previous project (automatically sliding it to the right) or after it.
Give the clip on Video 2 a distinctive look, like the effect you created in the first task. You can choose to apply one or more video effects or you can borrow what you came up with earlier (see tip).
To reuse an effect applied to a different clip:
Create a matte with a square black box (if you want to skip that Reverse Key thing, create a white box on a black background). The box should take up about the size of the object you want to highlight. No need to be precise. You'll use the Motion Settings dialog box to fine-tune it.
Just for a change of pace, in this exercise you may not want to use the Reverse Key box. Leaving it off means most of the screen will take on the video effect you applied to the clip on Track 2. Only the track matte box, which is going to follow the onscreen action, will have normal color. This, too, can be an excellent, eye-catching effect.
Import your matte to your project and drag it to Video 3. Extend it to match the length of your action clip.
Open the Transparency Settings dialog box for the clip on Video 2 and select Track Matte. If needed, click Reverse Key and preview your effect. As shown in Figure 16.9, there should be a box displaying your effect in the Sample screen.
The purpose here is to have the box follow the onscreen action. Open the Motion Settings dialog box for the track matte on Video 3. Make sure Show All and Alpha: Use Clip's are checked.
This is where things get a little tricky. You need to play and pause the clip in the preview window. With each pause, click the timeline to create a new handle. That puts a little highlight on the new handle in the Motion Path window to help you locate it.
Drag that new handle to center the track matte box over the object in motion. Do that until you have enough points to create a smooth path. As shown in Figure 16.10, I needed six handles in addition to the start- and endpoints to define a smooth path.
As the object moves through the frame, it probably changes size relative to the track matte box. You may need to gradually increase or decrease that box's area. Do that by clicking each handle within the timeline and changing the zoom percentage to adjust the box size. I've highlighted this in Figure 16.10. I changed mine from 50% to 130% over the duration of the clip.
That should do it. Preview your project. The square track matte should follow the action in your clip.
As with all things Premiere, there is another way to use a moving box to follow action: by using the Clip video effect. I'll give you a barebones explanation and leave the details for you to wrestle with.
Just as you did with a track matte, place identical clips on Video 1 and Video 2. Apply Clip to the clip on Video 2. Leave the default fill color black (you'll key it out later). As shown in Figure 16.11, turn on keyframes by clicking the empty box to the right of the f.
Figure 16.11. Using the Clip video effect with keyframes is another way to highlight an object?in motion or static.
Slide the edges of the screen in to form a box around the moving subject. Move the edit line forward a bit and adjust the box location. Do that enough times to create a smooth path for your moving box.
Open the Transparency Settings dialog box for the clip on Video 2, select Chroma Key, and use the Eyedropper tool to select the black border outside the clipped portion of your video clip.
As I've shown in Figure 16.12, there's no need to adjust the various sliders. Black keys out easily, and because you've applied a Tint effect to your clip, there should be no black in it that would become transparent.
Figure 16.12. There's no need to move the sliders because black keys out easily.