Apple Color 1.5 - Manual (Page 370)

The Tracking Tab
Motion tracking is the process of analyzing a shot in order to follow the motion of a
specific feature in the image to create a motion path. Once you’ve done this, you can use
these motion-tracked camera paths to animate secondary vignettes, Pan & Scan operations,
user shapes, and the Vignette node in the Color FX room to follow these motion paths.
This way, the corrections you make appear to follow moving subjects or the motion of
the camera.
There are actually two kinds of tracking:
• Automatic Tracking: Automatic tracking is ideal, as the computer analyzes part of the
image that you specify to follow a moving subject. This method creates a motion path
with a minimum of user input, but some shots may be difficult to track. When you
create an Automatic Tracker, a single onscreen control appears that consists of a pair
of boxes with crosshairs at the center.
When you process a tracker, Color analyzes an area of pixels specified by the outer
orange Search Region box of the onscreen control, over the range of frames specified
by the Mark In and Mark Out buttons. The tracker attempts to “follow” the feature
you’ve identified (using the inner red Reference Pattern box of the onscreen control)
as it moves across the frame. Angular, high-contrast features are ideal reference patterns
that will give you the best results.
• Manual Tracking: Manual tracking uses you as the computer, providing a streamlined
interface for you to follow a moving subject by clicking it with your mouse, frame by
frame from the In point to the Out point, until you’ve constructed a motion path by
hand. This method can be tedious, but it can also yield the best results for shots that
are difficult to track automatically.
You can use either one or both of these methods together to track a subject’s motion.
Note: Color can only use one-point motion tracking. Two- and four-point tracking are
not supported.
370 Chapter 15 The Geometry Room