Apple Motion 5.1.1 - Manual (Page 990)

Chapter 22 Motion tracking 990
Note: When the pointer is positioned over a tracker in the Canvas, a tool tip displays the start
frame for the tracking analysis. When you perform an offset track, the tool tip displays the frame
where the offset track began (if the playhead is in the range of the offset track).
Track retimed footage
When working in a project that includes tracking and retiming tasks, use the following guidelines
for more successful results:
•
Because the Motion tracker analyzes in a project’s frame rate, ensure that the frame rate of
the footage you plan to track matches the frame rate of the project. For example, to track 24
frames-per-second (fps) footage, your project’s frame rate should be 24 fps. When the tracking
analysis is completed, retime the clip using the Retiming parameters in the Media list or by
using the Retiming behaviors.
•
Do not retime the footage before the tracking analysis.
•
Do not retime the footage, perform a tracking analysis, then retime the footage again. This
may adversely affect your track.
Note: To track a clip after it is retimed, export the retimed clip, then import it back into your
project before you perform the tracking analysis.
Basic strategies to improve stabilization
The automatic motion analysis (analysis without trackers) used by the Stabilize behavior works
best with real images. Artificial images, such as those with no texture, are not recommended
for use with the Stabilize behavior’s automatic mode. Shots with very strong pans are also
not recommended.
Use the following techniques to improve the results of footage stabilization.
Add trackers to a portion of a stabilize operation
If a stabilized clip has a bumpy section that is not getting smoothed, you can add trackers
to noncontiguous sections of a clip. Any stabilize data from the automatic motion analysis is
overwritten by the portions of the clip analyzed using the onscreen trackers.
1 After the Stabilize motion analysis is complete, play the clip to determine the section you want
to track.
Important: Before adding any trackers, always review the entire clip. The Stabilize behavior needs
meaningful data—a large range of frames—to yield the best results.
2 Set an Out point for the tracker analysis: Position the playhead at the frame where you want to
stop the analysis, then choose Mark > Mark Play Range Out (or press Option-Command-O).
3 Position the playhead at the frame where you want to start the track, then do one of the
following:
•
To analyze X and Y position changes in the footage, click the Add button in the Inspector to
add an Anchor tracker.
•
To analyze changes in X and Y position as well as rotation and scale in the footage, click the
Add button two times to add the Anchor and Rotation-Scale trackers.
4 Position the newly added tracker on the reference pattern you want to track in the Canvas, then
click the Analyze button in the HUD or Inspector.
The specified play range is tracked, creating track points in the Canvas and tracking keyframes in
the Keyframe Editor.
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