 For image editing it is sometimes more convenient to simply go to the Curves dialog of the software, as it gives more flexibility in the shape of the curves.Or one can use Levels dialogue — the middle number is usually 1/γ, so one can just type 0.5.If one layer contains a homogeneous color, for example the gray color (0.8, 0.8, 0.8), multiply blend mode is equivalent to a curve which is simply a straight line.