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Why Track Motion?
Adobe After Effects motion tracking to underexposed footage allows you to track the movement of an object. This information can then be applied to another object, layer or effect. This creates the appearance that the other image or object is following the same path as the first image.
A good example of this is the Star Wars movies. The light saber followed the motion of the person, but the light source for the light saber was actually a separate image that left streaks in the air.
Another use for tracking the motion of an object is to stabilize the animation in the first layer. The second layer of movement will compensate for the movement occurring in the first layer. This second layer of motion will make the entire image more consistent.
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How to Track an Object's Motion
A layer is tracked by selecting a certain object or section of a frame. To track the motion of an object, follow the below procedures:
1. Select the object or layer that needs to be tracked. You can select this object in the video Timeline.
2. Next, select the Track Motion in Tracker panel.
3. Select Edit Target.
4. Select the area that needs to be tracked.
5. Pick the options for the keyframes, including scale, rotation and position.
6. Click on the Selection tool. Change the feature and search regions for the tracked object. You can also add a point for every track point.
7. Go to the Tracker panel. Here, select either Analyze Backward or Analyze Forward.
8. When ready to move forward, hit the Apply button.
The program will not start tracking the selected object. Always select a wide enough area that the entire object is selected throughout all of the clips. If not, the motion tracker will miss pieces of the object.
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How to Stabilize an Object
To stabilize an object, you should follow all the above rules, except steps two through four. Instead, go to the Tracker panel, and select the Stabilize Motion option. This will then track the source layer.
One problem with using the tracking feature on underexposed footage is that oftentimes the look of the shot changes dramatically. Lighting, angle and even other images around the object can change at any time. This makes it harder to track the object.
You can adjust your motion tracking to deal with this problem. To do this, follow the below steps:
1. Stop the tracking.
2. Move the current-time indicator to the frame where the object was still being correctly tracked.
3. Go to the Tracker panel, and select Options.
4. Adjust the Motion Tracker settings.
5. Go back to the Tracker panel, and select either Analyze Backward or Analyze Forward.
6. Click Apply.
The Motion Tracker will start tracking the object again. Keep watching the motion to ensure that it is tracking the object properly. If not, you should stop the action again and modify the Motion Tracker settings further.