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The
Chroma Key effect creates transparency from a color or range of
colors. You can use this key for a scene shot against a screen that
contains a range of one color, such as a shadowy blue screen. Select
a key color by clicking the Color swatch or by clicking the Eyedropper
tool and selecting a color in the Monitor panel. Control the range
of transparent colors by adjusting the tolerance level. You can
also feather the edges of the transparent area to create a smooth transition
between the transparent and opaque areas.
View full size graphic Chroma Key - A.
- Original clip
- B.
- Blue color
keyed out
- C.
- Clip on second track
- D.
- Final
composite clip
 Apply the Chroma Key effect to a clip multiple
times to key out multiple colors. Adjust the following
Chroma key settings as needed:
- Similarity
- Broadens or reduces the range of color that will be made
transparent. Higher values increase the range.
- Blend
- Blends the clip you are keying out with the underlying clip.
Higher values blend more of the clip.
- Threshold
- Controls the amount of shadows in the range of color you
keyed out. Higher values retain more shadows.
- Cutoff
- Darkens or lightens shadows. Drag to the right to darken
shadows, but do not drag beyond the Threshold slider; doing so inverts
gray and transparent pixels.
- Smoothing
- Specifies the amount of anti‑aliasing applied to the boundary between
transparent and opaque regions. Anti‑aliasing blends pixels to produce softer,
smoother edges. Choose None to produce sharp edges with no anti‑aliasing.
This option is useful when you want to preserve sharp lines, such
as those in titles. Choose Low or High to produce different amounts
of smoothing.
- Mask Only
- Displays only the clip’s alpha channel, as modified by the
key settings. If Mask Only is selected, opaque areas of a clip appear
white, transparent areas appear black, and partially transparent
areas appear gray. Remove all the gray areas to produce a clean,
hard‑edged key.
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