When you key an image that was shot against a blue screen or green screen, some color will have reflected from the screen to illuminate the edges, or even the interior, of the foreground subject. This unwanted coloration of the subject is called spill, and can be difficult to eliminate from the foreground subject you’re trying to preserve.
Unlike the spill suppression controls found in the Keyer filter, which automatically neutralize the color being keyed, the Spill Suppression filter lets you deal with this problem by manually choosing the color to be neutralized. After you apply a Spill Suppression filter, you can adjust its controls in the Filters Inspector:
Color: A color control to sample the color to suppress. Click the color well and choose a hue from the Colors window, or use the eyedropper to sample a color in the Canvas.
Level: A slider to adjust the amount of spill removal applied to the keyed image.
Tip: Green screen clips typically benefit from a lower spill-level setting than blue screen clips. Good starting points to try are 46% for green and 73% for blue, although you’ll need to customize these values for your composites.
Spill Contrast: A grayscale gradient control to adjust the contrast of the color being suppressed, using Black point 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 control) lightens edge fringing that’s too dark. The White point handle (on the right side of the 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: A slider to restore the natural color of the keyed foreground subject. Because 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: A slider to alter the range of hues introduced by the Tint slider (when the Tint slider is used at moderate levels).
Tip: The best order in which to use these controls is to adjust Tint before you adjust Saturation.
Mix: A slider to set the percentage of the original image to be blended with the filtered image. 100% is the filtered image, while 0% is the original, unfiltered image.