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The original documentation was a little less informative so as to fully describe what an RGB curve does. Does it maximize the color of texture? Or, are the x and y coordinates equivalent to input and output level like in Gimp? And how do the seperate channel's curve work out?

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  • $\begingroup$ It works exactly like GIMP afaik. GIMP even has separate curves for each channel, just like blender. $\endgroup$ – gandalf3 Dec 7 '15 at 10:01
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Via RGB Curves node (whether Cycles or Compositor) you can adjust contrast, gamma, gain and also offset adjustments. The displayed curve refer to a given color input brightness. The horizontal axis represents the input values, and the vertical axis represents the output values.

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Enable C (Composite) to adjust RGB channels simultaneously. Enable R, G, or B if you want to limit the adjustment to a particular color channel.


Also see the manual:

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    $\begingroup$ This is a good answer worth also examining white point and black point. Bear in mind that Cycles is a scene referred imaging model as opposed to display referred. That means that values extend from zero to infinity. One is able to use the white and black points to map part of that infinite range to the display referred output transform. Try it by putting ten or so lights very close to the default cube and using the white and black points to creatively control the display referred output. This is in contrast to display referred imaging applications like GIMP. $\endgroup$ – troy_s Jan 5 '16 at 3:47
  • $\begingroup$ @troy_s Thanks Troy :) Yep, I know that there is a lot to cover, but my intention was to focus on the curve itself to get a basic understanding what it does and how to use it. I don't have the time right now, but I also want to add some basic color operation examples, introducing the term of Lookup Table and more. But feel free to edit my answer - I'd really appreciate it. $\endgroup$ – p2or Jan 5 '16 at 10:49
  • $\begingroup$ I edited the link because it was broken but actually the two links point to the same content, which is a bit misleading because the cycles node doesn't have the black and white levels $\endgroup$ – qwazix Jan 14 '17 at 10:02

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