Adobe 65008009 - After Effects CS4 Using Manual page 281

Last updated 12/21/2009
To change the format in which color values are shown in the Info panel and in some effect controls, choose an option
such as Percent or Web from the Info panel menu. Choosing Auto Color Display automatically switches between 8
bpc, 16 bpc, and 32 bpc, depending on the color depth of the project.
Though many effects can work with all color depths, some effects work only with lower color depths. You can set the
Effects & Presets panel to only show effects that work with your current project color depth. (See
panel" on page 392.)
Comparative advantages of each color depth
The dynamic range (ratio between dark and bright regions) in the physical world far exceeds the range of human vision
and of images that are printed on paper or displayed on a monitor. Low dynamic range 8-bpc and 16-bpc color values
can represent RGB levels only from black to white, which is only a small segment of the dynamic range in the real
world.
High dynamic range (HDR), 32-bpc floating-point color values can represent brightness levels much greater than
white, including objects as bright as a flame or the Sun.
Set the project color depth to 32 bpc to work with HDR footage or to work with over-range values—values above 1.0
(white) that aren't supported in 8- or 16-bpc mode. Over-range values preserve the intensity of highlights, which is as
useful for synthetic effects such as lights, blurs, and glows as it is for working with HDR footage. The headroom
provided by working in 32 bpc prevents many kinds of data loss during operations such as color correction and color
profile conversion. Even if you're using 8-bpc footage and are creating movies in 8-bpc formats, you can obtain better
results by having the project color depth set to 16 bpc or 32 bpc. Working in a higher bit depth provides higher
precision for calculations and greatly reduces quantization artifacts, such as banding in gradients.
Glow effect and Gaussian Blur effect applied to image in 32-bpc project (left) and 16-bpc project (right)
Because 16-bpc frames use half the memory of 32-bpc frames, rendering previews in a 16-bpc project is faster, and
RAM previews can be longer than in a 32-bpc project. 8-bpc frames use even less memory, but the tradeoff between
quality and performance can be obvious in some images at a project color depth of 8 bpc.
Special considerations for working with high dynamic range color
You can use the HDR Compander effect to compress the dynamic range of a layer with an HDR footage item as its
source. In this way, you can use tools that don't support HDR color, such as 8-bpc and 16-bit effects. When you're
done, use the HDR Compander to undo the dynamic range compression. The HDR Highlight Compression effect lets
you compress the highlight values in an HDR image so that they fall within the value range of a low dynamic range
image.
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USING AFTER EFFECTS CS4
Color
"Effects & Presets