Here is what I want to achieve. Let's say I have base layer which is some photo. I'll make a copy of it and apply Shadows/Highlights filter on it.
How would you produce 18%-grey-filled layer from these two layers so that application of this new layer to base layer in Overlay mode would produce close effect as Shadows/Highlights filter ?
I know dodge/burning with overlay layer give saturation shifts but let's say it's not a problem in this case.