Adobe AFTER EFFECTS CS3 PROFESSIONAL User Manual page 548

Because the first instance of the HDR Compander effect compresses the range of values through sampling, some
precision is lost. For this reason, use the HDR Compander effect only if you're willing to trade off some precision in
values for the sake of high dynamic range.
This effect works with 8-bpc, 16-bpc, and 32-bpc color.
See also
"High dynamic range color" on page 235
"Set the color depth" on page 234
Apply the HDR Compander effect
1 Apply the HDR Compander effect to a layer in a 32-bpc project.
Select Compress Range for Mode.
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Set Gain to the maximum value to be represented in the compressed range—that is, the highest white value in the
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image. Don't set Gain too high; the more of the 16-bpc value that you use for highlights, the more compressed the
midtones (the majority of the pixels) will be, and the more data will be lost in this process.
Set Gamma. Gamma affects the distribution of values in the range, allowing more precision in specific areas of
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the range.
5 Apply whatever low-dynamic-range effects you choose to the layer.
Apply another instance of the HDR Compander effect to the layer. Make sure that the second instance of HDR
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Compander is ordered after (below) any 8-bpc or 16-bpc effects you've applied.
Select Expand Range for Mode for the second instance of the HDR Compander effect.
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Set Gain and Gamma to the same values as set in the first instance of the HDR Compander effect.
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A more convenient way to use the HDR Compander effect is to apply the Compress-Expand Dynamic Range
animation preset. This animation preset consists of an expression and two instances of the HDR Compander effect:
The first instance has Compress Range selected, and the second has Expand Range selected. The expression automati-
cally sets the Gain and Gamma for the second instance to be the same as that which you set for the first instance. Insert
whatever low-dynamic-range effects you choose between these two instances of the HDR Compander effect.
HDR Highlight Compression effect
The HDR Highlight Compression effect compresses the highlight values in a high–dynamic range image so that they
fall within the value range of a low-dynamic-range image. Adjust the amount of compression by setting the effect's
Amount property.
See also
"High dynamic range color" on page 235
"Set the color depth" on page 234
AFTER EFFECTS CS3 542
User Guide