Quote Originally Posted by Thomas Bertilsson View Post
While I agree with you about getting 'something' from 'nothing', the case is usually that a lot of the 'lost' shadow detail ends up on the toe of the film curve, lost in 'film base plus fog' density. By under exposing film on purpose, and over developing, some of that shadow detail on the toe can be 'pushed' back up onto a portion of the curve, where it's no longer obscured by the densities of film base plus fog.
Some developers are better than others at this, and this is why dilute developers, like Xtol 1+1 is better than stock - longer developing time brings out more shadows. Not a fantastic amount, but it does help, and it is real.
I put in the word "moreso" because I do realize that if it's in there longer, shadows will come out a bit more, but then you'll blow your highlights way out of proportion by overdeveloping. Shadows stop developing first in the developing process and after a point, they are incredibly difficult to budge without blowing out your highlights.

That being said, I'm not sure how the logic of under exposing and over developing can bring out shadow details can be consistent. There would be less density in the shadows in that case.