About rgb difference key, About blue screen key – Adobe Premiere Pro CS3 User Manual
Page 377
ADOBE PREMIERE PRO CS3
User Guide
371
See also
About RGB Difference Key
The RGB Difference Key is a simpler version of the Chroma Key. It lets you select a range for the target
color, but
you cannot blend the image or adjust transparency in grays. Use the RGB Difference Key for a scene that is brightly
lit and contains no shadows, or for rough cuts that don’t require fine adjustments.
Note: The Difference Matte uses a matte to define the alpha channel much as the RGB Difference Key uses a color.
The following RGB Difference Key settings are adjusted in the Effect Controls panel:
Color
Specifies the color in the video that will be made transparent by the mask.
Similarity
Broadens or reduces the range of the target color that will be made transparent. Higher values
increase
the range.
Smoothing
Specifies the amount of anti-aliasing (softening) that Adobe Premiere Pro applies 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.
Drop Shadow
Adds a 50% gray, 50% opaque shadow offset 4 pixels down and to the right from the opaque areas of
the original clip image. This option works best with simple graphics such as titles.
See also
About Blue Screen Key
The Blue Screen Key creates transparency from true chroma blue. Use this key to key out well-lit blue screens when
creating composites.
The following Blue Screen Key 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.
April 1, 2008