Is there any way to adjust contrast without affecting overall brightness? For example, when modifying a displacement map I need to be able to change the tonal range uniformly so that the darks get darker, the lights get lighter and 50% grey stays at 50%. The Brightness/Contrast curve provides no accuracy for this.

Thanks,

(c:

With Levels command you should be able to empirically compensate the midtones levels to stay at 50%.
lets say you move the white point 15 units to the left and the black 10 units to the right, the midtone point should then be moved 5 points to the right (-10+15=+5). Theorically.
For reasons I don't know I noticed I have to reduce the midtone point of 2 units to get the right value (in this case +3 units to the right and a 127% grey colour will stay at 127% after the Levels command).

Hope this works for you.

Hi Azzart,

Thanks for the suggestion - I tried Levels though and it's just as much a guessing game as with Brightness/Contrast curve. If I add 50 to black and subtract 50 from white for example, I find after some trial and error that the midtone has to be set at 0.92...

(c: