Adobe 65021048 User Guide - Page 377

ADOBE PREMIERE PRO CS3 371 User Guide See also "Chroma Key effect" on page 335 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 "RGB Difference Key effect" on page 338 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