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I was playing with curves a little bit (CS2) and got a strange effect when I applied an admittedly rather uncommon curves transformation to a monochrome gradient. You can see the result at:
http://tinyurl.com/8xh98
the image displayed links to the actual PS file with the gradient layer still in place, which you may download for inspection. The bottom left part shows how the image looked like at the beginning and the top right what I got after adding my contrived curves layer. You will find that the gradient is made up between two colors with exactly the same hue and saturation, and with brightness varying between zero and 100%. Since I did not modify individual color channels I’d have expected a result which is actually obtained when the curves layer blending mode is set to luminosity. This is what I do routinely to prevent unwanted changes in saturation.
What I got here is really surprising to me, since there is not only a change in saturation as expected but also in hue. It looks to me as if there were some serious rounding or overflow error in the curves routine.
BTW, I opened the file in CS and 7 as well and it looked always the same.
Please share your opinion
Peter
http://tinyurl.com/8xh98
the image displayed links to the actual PS file with the gradient layer still in place, which you may download for inspection. The bottom left part shows how the image looked like at the beginning and the top right what I got after adding my contrived curves layer. You will find that the gradient is made up between two colors with exactly the same hue and saturation, and with brightness varying between zero and 100%. Since I did not modify individual color channels I’d have expected a result which is actually obtained when the curves layer blending mode is set to luminosity. This is what I do routinely to prevent unwanted changes in saturation.
What I got here is really surprising to me, since there is not only a change in saturation as expected but also in hue. It looks to me as if there were some serious rounding or overflow error in the curves routine.
BTW, I opened the file in CS and 7 as well and it looked always the same.
Please share your opinion
Peter
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