Adobe After Effects CS4 - Manual (Page 453)

447 USING AFTER EFFECTS CS4
Effects and animation presets
Last updated 12/21/2009
Channel effects
Additional resources about Channel effects
Satya Meka provides the Separate RGB effect plug-in on the After Effects Scripts website . This effect—which was
written with Pixel Bender—offsets, scales, and rotates each color channel of an image separately.
Alpha Levels effect
If you are working on a project that was created in an older version of After Effects and the Alpha Levels effect is
applied to one or more layers, you can continue to use the Alpha Levels effect; otherwise, use the Levels effect with
Channel set to Alpha. The Levels effect can process the full range of 32-bpc channels, and it provides a histogram
control, which the Alpha Levels effect lacks. (See “
Levels effect ” on page 465.)
This effect works with 8-bpc and 16-bpc color.
Arithmetic effect
The Arithmetic effect performs various simple mathematical operations on the red, green, and blue channels of an
image.
This effect works with 8-bpc color.
Operator The operation to perform between the value you specify for each channel and the existing value of that
channel for each pixel in the image:
• And, Or, and Xor Apply bitwise logical operations.
• Add, Subtract, Multiply, and Difference Apply basic math functions.
• Max Set the channel value of the pixel to the greater of the specified value and the original value of the pixel.
• Min Set the channel value of the pixel to the lesser of the specified value and the original value of the pixel.
• Block Above Set the channel value of the pixel to zero if the original value of the pixel is greater than the value
specified; otherwise, leave the original value.
• Block Below Set the channel value of the pixel to zero if the original value of the pixel is less than the value specified;
otherwise, leave the original value.
• Slice Set the channel value of the pixel to 1.0 if the original value of the pixel is above the specified value; otherwise,
set the value to zero. In both cases, the values for the other color channels are set to 1.0.
• Screen Multiplies the complements of the channel values, and then takes the complement of the result. The result
color is never darker than either input color.
Clip Result Values Prevents all functions from creating color values that exceed the valid range. If this option isn’t
selected, some color values may wrap around.
Blend effect
The Blend effect blends two layers using one of five modes.
You can blend layers more easily and quickly using blending modes, but you can’t animate blending modes. The
advantage of using the Blend effect is that you can animate it. (See “
Blending modes and layer styles ” on page 171.)