Gamma correction is a more general technique than log rescale. It is related in the way it works, but there is a parameter called Gamma that controls the exact shape of the curve.
A gamma less than one will increase the brightness of mid-intensity pixels, and de-emphasize brighter pixels. A gamma greater than one will have the opposite effect.
Before and After Gamma
Mathematically, gamma is expressed by:
Out = Input g
Often gamma is used as a final ”tweak”, to punch up the image a little, or to pull back if the previous processing was a little too aggressive. Gamma can be adjusted using the Process menu Stretch command and the Process menu Levels command.