Adobe Premiere Pro CS4 - Manual (Page 382)

376 USING ADOBE PREMIERE PRO CS4
Effects and transitions
Last updated 11/6/2011
The following Blue Screen Key effect settings are adjusted in the Effect Controls panel:
Threshold Sets the levels of blue that determines transparent areas in a clip. Dragging the slider to the left increases
the amount of transparency. Use the Mask Only option to view black (transparent) areas as you drag the Threshold
slider.
Cutoff Sets the opacity of nontransparent areas specified by the Threshold setting. Dragging the Cutoff slider to the
right increases the opacity. Use the Mask Only option to view white (opaque) areas as you drag the Cutoff slider.
Smoothing Specifies the amount of anti-aliasing (softening) applied to the boundary between transparent and opaque
regions. 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. Black represents transparent areas, white represents opaque areas,
and gray represents partially transparent areas.
Subject is photographed against blue background (left). Blue Screen Key effect is applied (right) to superimpose subject over underlying track.
For more information about using blue screen and green screen effects, see the Metacafe website .
Chroma Key effect (Windows only)
The Chroma Key effect keys out all image pixels that are similar to a specified key color. When you key out a color
value in a clip, that color or range of colors becomes transparent for the entire clip. 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.
Chroma Key effect
A. Original image B. Blue color keyed out C. Image on second track D. Final composite image
The following Chroma Key effect settings are adjusted in the Effect Controls panel:
Similarity Broadens or reduces the range of the target 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 that Premiere Pro applies to the boundary between transparent and
opaque regions. Anti-aliasing blends pixels to produce softer, smoother edges. Choose None to produce sharp edges,
A B C D