Adobe After Effects CS3 - Manual (Page 448)

AFTER EFFECTS CS3
User Guide
443
See also
“Keying overview and tips” on page 268
“Matte Choker effect” on page 450
“Simple Choker effect” on page 451
Use the Color Range effect
1 Select the layer you want to make transparent, and then choose Effect > Keying > Color Range.
2 Choose Lab, YUV, or RGB from the Color Space menu. If you have trouble isolating the subject using one color
space, try using a different one.
3 Select the Key Color eyedropper, and then click in the matte thumbnail to select the area that corresponds to a
color in the Composition panel you want to make transparent. Typically, this first color is the one that covers the
largest area of the image.
Note: To use the eyedroppers in the Layer panel, choose Color Range from the View menu in the Layer panel.
4 Select the Plus eyedropper, and then click other areas in the matte thumbnail to add other colors or shades to the
range of colors keyed out for transparency.
5 Select the Minus eyedropper, and then click areas in the matte thumbnail to subtract other colors or shades from
the range of colors keyed out.
6 Drag the Fuzziness slider to soften the edges between transparent and opaque regions.
7 Use the sliders in the Min/Max controls to fine-tune the color range you selected with the Plus and Minus
eyedroppers. The L, Y, R sliders control the first component of the specified color space; the a, U, G sliders control
the second component; and the b, V, B sliders control the third component. Drag the Min sliders to fine-tune the
beginning of the color range. Drag the Max sliders to fine-tune the end of the color range.
Difference Matte effect
The Difference Matte effect creates transparency by comparing a source layer with a difference layer, and then keying
out pixels in the source layer that match both the position and color in the difference layer. Typically, it’s used to key
out a static background behind a moving object, which is then placed on a different background. Often the difference
layer is simply a frame of background footage (before the moving object has entered the scene). For this reason, the
Difference Matte effect is best used for scenes that have been shot with a stationary camera and an unmoving
background.
This effect works with 8-bpc and 16-bpc color.