Basically, the curves tool gives you a line from 0,0 to 256,256, meaning that anything at a darkness of 0 will be converted to a darkness of 0 after applying the curves tool, and so on. Then you can push and pull the line -- it tries to make it a spline curve so it'll be smoothed -- until it leaves your picture nicely dark where you want it to be dark, and white where you want it to be white.
Typically, I'll make it an S-shaped curve with the lower and upper ends of the S pressed against the bottom and top respectively to have pure white and black; the sloping part will be more steep and narrow if I am scanning an ink picture, to create almost pure B&W, and about a 60-degree diagonal if I'm doing grayscale.
You could also, for instance, flip the curve to be 256,0 to 0,256 to make it invert black and white, for some striking effects.
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timeasmymeasure
no subject
Date: 2003-05-27 11:37 am (UTC)Typically, I'll make it an S-shaped curve with the lower and upper ends of the S pressed against the bottom and top respectively to have pure white and black; the sloping part will be more steep and narrow if I am scanning an ink picture, to create almost pure B&W, and about a 60-degree diagonal if I'm doing grayscale.
You could also, for instance, flip the curve to be 256,0 to 0,256 to make it invert black and white, for some striking effects.