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The Black Stretch option remaps the low pixel values of all channels. Large Black Stretch
values brighten dark areas. The effect is the same in all quality settings. Gamma specifies
an exponent describing the shape of the intermediate curve. The Pedestal and Gain
options specify the lowest and highest attainable output value for a channel.
Median
This effect replaces each pixel with the median pixel value of neighboring pixels within a
given radius. At low values, this effect is useful for reducing some types of noise. At higher
values, this effect gives a layer a painterly effect. This effect is the same at both Draft and
Best quality. Use Radius to specify how many pixels to examine for the Median effect. For
instance, when Radius is set to 1, the Median is performed on the eight neighboring pixels
that are within one pixel of the center pixel.
PS Arbitrary Map
This effect applies an Adobe Photoshop arbitrary map file to a layer. An arbitrary map
adjusts the brightness levels of an image, remapping a specified brightness range to
darker or brighter tones. It is intended only to provide compatibility with projects created
in earlier versions of After Effects that use the Arbitrary Map effect. For new work, use the
Curves effect.
For more information, see the After Effects product section on Adobe's Web site.
Tint
This effect alters an image's color information. For each pixel, the luminance value
specifies a blend between two colors. Map Black To and Map White To specify the colors to
which dark and bright pixels are mapped. Intermediate pixels are assigned intermediate
values. Amount to Tint specifies the intensity of the effect. The layer's quality setting does
not affect Tint. For more complex tinting, use the Colorama effect.
Keying effects
Use these effects to key out (make transparent) parts of an image. For more information
on using keying effects, see "Creating track mattes and traveling mattes" on page 164.
After Effects includes two basic keying effects. The Production Bundle includes seven
additional, more powerful keying effects.
Color Difference Key (PB only)
This Key creates transparency from opposite starting points by dividing an image into two
mattes, Matte Partial A and Matte Partial B. Matte Partial B bases the transparency on the
specified key color, and Matte Partial A bases transparency on areas of the image that do
not contain a second, different color. By combining the two mattes into a third matte,
called the alpha( ) matte, the Color Difference Key creates well-defined transparency
values.
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Applying Effects
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