Role of Opacity in Difference Blend Mode

GA
Posted By
George_Austin
Aug 1, 2006
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878
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0
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Closed
When two white layers (color channels at 255) each at 50% opacity are blended in Difference mode, the blend result is 170 in each channel.

Question: Whence 170???

Comment: If either layer is at 100% opacity, the blend result is a linear function of the other layer’s opacity. Therefore, I would have expected the result to be a linear function of the product of the opacities when neither opacity is 100% so that, in the example cited, the result would have been 192 rather than 170 (255 – 0.5 x 0.5 x 255 = 255 – 64 = 192).

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