Adobe Premiere Pro CS6 - Manual (Page 414)

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, 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.
Chromakey with the Ultra Key effect
Karl Soule provides an overview of the Ultra Key effect on the Adobe website .
Tracy Peterson provides a video tutorial that demonstrates the Ultra Key effect on the Adobe website .
Will Head of MacUser shows tips and tricks for keying using the Ultra Key effect here .
For more information about creating key effects with the Ultra key in Premiere Pro, see this video by Video2Brain by Jan Ozer.
Eran Stern shows you how to use the Ultra Key effect in this tutorial .
The Ultra Key effect is GPU accelerated, for improved playback and rendering performance, in computers with a supported nVIDIA card.
1. Apply Ultra Key to a clip or clips.
2. In the Timeline, place the current-time indicator over a frame containing a key color.
3. In the Effect Controls panel, select the desired options from the Output and Setting menus.
4. Do one of the following:
Click the Color Picker box to open the Color Picker. Then select a key color and click OK.
Click the Eye Dropper, and select a key color.
Set the other parameters as desired.
Ultra Key effect parameters
Matte Generation
Transparency Controls the transparency of the source when keyed over a background. Values range from 0 through 100. 100 is fully transparent.
0 is opaque. The default value is 45.
Highlight Increases the opacity of light areas of the source image. You can use Highlight to extract details like specular highlights on transparent
objects. Values range from 0 through 100. The default value is 50. 0 does not affect the image.
Shadow Increases the opacity of dark areas of the source image. You can use Shadow to correct a dark element that became transparent
because of color spill. Values range from 0 through 100. The default value is 50. 0 does not affect the image.
Tolerance Filters out colors in the foreground image from the background. Increases tolerance to variation from the key color. You can use
Tolerance to remove artifacts caused by color shift. You can also use Tolerance to control spill on skin tones and dark areas. Values range from 0
through 100. The default value is 50. 0 does not affect the image.
Pedestal Filters out noise, often caused by grainy or low light footage, from the alpha channel. Values range from 0 through 100. The default
value is 10. 0 does not affect the image. The higher the quality of your source image, the lower you can set Pedestal.
Matte Cleanup
Choke Shrinks the size of the alpha channel matte. Performs a morphological Erode (fractional kernel size). Choke Level Values range from 0
through 100. 100 represents a 9x9 kernel. 0 does not affect the image. The default value is 0.
Soften Blurs the edge of the alpha channel matte. Performs a box blur filter (fractional kernel size). Blur Level values range from 0 through 100. 0
does not affect the image. The default value is 0. 1.0 represents a 9x9 kernel.
Contrast Adjusts the contrast of the alpha channel. Values range from 0 through 100. 0 does not affect the image. The default value is 0.
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