sure. first off, you can check the blend file:

http://www.pasteall.org/blend/36118

now, RGB curves node: this is my setup

i noticed that most of the colors in the image are in the range of vlaues (as in hue-saturation-value) of 0-0.2. this node allows me to tweek those values. X axis is the input image. Y axis is the modified image, after applying the curve. in this case, i added 2 control points in the lower left corner of the curve. the first one is at position (x=0.05, y=0.02), which means it takes all pixels of value 0.05 and lowers them to value 0.02; also, all pixels of values smaller than 0.05 will be lowered by the curve as well (all of them will be smaller than 0.02 after this node), in accordance with the shape of the curve.

the second point is in position (x=0.12, y=0.15), which means it takes all pixels who’s values are higher than 0.05 (the first point location on the x axis) and raises them according to the curve. in particular, all pixels of value 0.12 will be raised to value 0.15.

in effect, all pixels of values between 0.05 and 0.12 are stretched to the range 0.02 and 0.15, while values lower than 0.05 are “squashed” (values higher than 0.12 are also somehwat squashed).

i hope i haven’t confused you to much so far. :eek:

the nice thing about rgb curves is that you can create gradients of transition, so that all those stretching and squashing of values are not shrap (which would make them noticable), but gradual.

next up: hue correct