Apple Motion 5.1.1 - Manual (Page 507)

Chapter 13 Keying 507
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Black, White, Bias: Click the disclosure triangle in the Levels row to reveal sliders for the Black,
White, and Bias parameters. These sliders, which mirror the settings of the Levels handles
described above, allow you to keyframe and apply Parameter behaviors to the three Levels
parameters (via the Add Keyframe button to the right of each slider). Keyframing the Black,
White, and Bias parameters may yield a better key, one that adapts to changing blue screen or
green screen conditions.
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Shrink/Expand: Use this slider to manipulate the contrast of the matte to affect matte
translucence and matte size simultaneously. Drag the slider left to make translucent regions
more translucent while simultaneously shrinking the matte. Drag the slider right to make
translucent regions more solid while simultaneously expanding the matte.
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Soften: Use this slider to blur the keyed matte, feathering the edges by a uniform amount.
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Erode: Drag this slider to the right to increase edge transparency from the outer edge of the
matte progressively further into the interior of the keyed matte.
Light Wrap controls
Click the disclosure triangle in the Light Wrap row to reveal controls for blending color and
lightness values from the background layer of your composite with the keyed foreground layer.
Using these controls, you can simulate the interaction of environmental lighting with the keyed
subject, making it appear as if background light wraps around the edges of a subject. In Motion,
the Light Wrap operation blends light and dark values from the background with the edges
of the keyed foreground subject, and can be used to create color mixing effects around the
edges of the solid part of a key to better marry the background and foreground layers of your
keyed composite.
Light Wrap is the last operation in the image-processing pipeline. In other words, the light-
wrap effect is added after every other image operation is processed, including filters, lights and
shading, and other composited effects. As a result, Light Wrap accounts for any visual effect that
might alter the look of the object it is applied to, yielding the most desirable result.
Important: A separate Light Wrap option appears in the Blend Mode pop-up menu of the
Properties Inspector for a selected layer or group in Motion. The Light Wrap blend mode in the
Properties Inspector for a layer is ignored when you add a Keyer filter to that layer and set the
Light Wrap Amount parameter to a value greater then 0. (The Light Wrap parameters of the
Keyer filter take precedence.) However, if you set the Amount parameter of the Light Wrap group
to 0, the Light Wrap blend mode becomes active again. Further, the Light Wrap blend mode in
the Properties Inspector for a group overrides the Light Wrap parameters of any Keyer filters in
that group.
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Amount: Use this slider to control the light-wrap effect, setting how far into the foreground the
light wrap extends.
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Intensity: Use this slider to adjust gamma levels to lighten or darken the interaction of
wrapped edge values with the keyed foreground subject.
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Opacity: Use this slider to fade the light wrap effect up or down.
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Mode: Use this pop-up menu to choose the compositing method to blend the sampled
background values with the edges of the keyed subject. There are five modes:
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Normal: Evenly blends light and dark values from the background layer with the edges of
the keyed foreground layer.
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Lighten: Compares overlapping pixels from the foreground and background layers, then
preserves the lighter of the two. Good for creating a selective light wrap effect.
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