This probably applies to Photoshop too. The question is how do you get a photo of a drawing to look like the drawing? I've been trying to get it but only end up with grotesquely mutated versions of what originally was a reasonably delicate shading job. Doesn't help that the drawing photographed rather lightly - it looks like that might be a common trait of graphite.
Trying to bump the contrast at all just kills it so far and playing with the curves so far hasn't helped, but I'm probably a retard at that.