Apple Motion 5.1.1 - Manual (Page 495)

Chapter 13 Keying 495
Spill Suppression controls
Click the disclosure triangle in the Spill Suppression row to reveal controls for neutralizing a
colored light that bounces off the blue screen or green screen and contaminates the isolated
foreground subject. This fringing around the edge of the subject is called spill, and is difficult to
eliminate because it’s part of the subject you’re trying to preserve.
The Spill Suppression controls work by letting you adjust the color correction that neutralizes
unwanted color in the foreground subject. While the Spill Level slider (described above) controls
how much suppression is applied, the controls in this group let you customize the quality of
suppression being performed.
When first applied, the Keyer filter adds spill suppression to the video clip or image, based on the
dominant color sampled to create the initial key. This automatic spill suppression desaturates the
key color so fringing around the foreground subject appears gray (rather than blue or green). But
if you reduce the Spill Level slider to 0, effectively turning off spill suppression, the gray fringing
turns blue or green (the color of your background), proving that successful spill suppression is
rendering the background a neutral gray.
The Spill Suppression group contains the following controls:
•
Spill Contrast: Use this grayscale gradient to adjust the contrast of the color being suppressed,
using Black and White point handles (and corresponding sliders). Modifying spill contrast can
reduce the gray fringing surrounding a foreground subject. The Black point handle (on the left
side of the gradient control) lightens edge fringing that is too dark for a successful composite.
The White point handle (on the right side of the gradient control) darkens edge fringing that
is too light. Depending on how much spill is neutralized by the Spill Level slider, these controls
may have a greater or lesser effect on the subject.
•
Black, White: Click the disclosure triangle in the Spill Contrast row to reveal sliders for the
Black and White point parameters. These sliders, which mirror the settings of the Spill Contrast
handles described above, allow you to keyframe the Black point and White point parameters
(via the Add Keyframe button to the right of each slider).
•
Tint: Use this slider to restore the natural color of the keyed foreground subject. Because the
Spill Suppression controls eliminate blue or green spill by desaturating subtle blue or green
fringing and reflection on the subject, the Tint slider lets you add hues to restore the natural
color of the subject. Overdoing this parameter results in over-tinting the subject with the
complementary color of the hue being suppressed—magenta if green, and orange if blue.
•
Saturation: Use this slider to alter the range of hues introduced by the Tint slider (when the
Tint slider is used at moderate levels).
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