Adobe Premiere Pro CS6 - Manual (Page 418)

White background of original (top and left) is removed using the Luma Key effect and composited over underlying layer (right).
Adjust the following settings as necessary:
Threshold Specifies the range of darker values that are transparent. Higher values increase the range of transparency.
Cutoff Sets the opacity of nontransparent areas specified by the Threshold slider. Higher values increase transparency.
You can also use the Luma Key effect to key out light areas by setting Threshold to a low value and Cutoff to a high value.
Non Red Key effect
The Non Red Key effect creates transparency from green or blue backgrounds. This key is similar to the Blue Screen Key effect, but it also lets
you blend two clips. In addition, the Non Red Key effect helps reduce fringing around the edges of nontransparent objects. Use the Non Red Key
effect to key out green screens when you need to control blending, or when the Blue Screen Key effect doesn’t produce satisfactory results.
The following Non Red Key effect settings are adjusted in the Effect Controls panel:
Threshold Sets the levels of blue or green that determine transparent areas in the clip. Dragging the Threshold slider to the left increases the
amount of transparency. Use the Mask Only option to view the black (transparent) areas as you move the Threshold slider.
Cutoff Sets the opacity of nontransparent areas specified by the Threshold slider. Higher values increase transparency. Drag to the right until the
opaque area reaches a satisfactory level.
Defringing Removes residual green or blue screen color from the edges of the opaque areas of a clip. Choose None to disable defringing.
Choose Green or Blue to remove a residual edge from green-screen or blue-screen footage, respectively.
Smoothing Specifies the amount of anti-aliasing (softening) that 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.
RGB Difference Key effect (Windows only)
The RGB Difference Key effect is a simpler version of the Chroma Key effect. 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 effect 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 effect uses a matte to define the alpha channel much as the RGB Difference Key effect uses a color.
The following RGB Difference Key effect 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 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.
Remove Matte effect
The Remove Matte effect removes color fringes from clips that are premultiplied with a color. It is useful when combining alpha channels with fill
textures from separate files. If you import footage with a premultiplied alpha channel, or if you create alpha channels with After Effects, you may
need to remove halos from an image. Halos are caused by a large contrast between the image's color and the background, or matte, color.
Removing or changing the color of the matte can remove the halos.
Use Background Color to specify the new background color when you want to change the color of a matte.
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