Basically, Nolan shot complementary takes of Eckhart in Two-Face makeup so he could visually represent the duality of Dent in a less cartoony fashion. What Nolan’s doing doesn’t sound all that far removed from the Gollum/Smeagol model, though the obvious difference here is that Dent isn’t motion-capture; he’s a fifty-fifty split of the same actor giving two wildly divergent performances in the same shot. And because he has two takes of each scene, Nolan has the luxury of shaping Eckhart’s performance in post; it’s just a matter of switching the dial between normal Harvey and bug-fuck Two-Face. Again, both will be present in the shot, but only one will dominate the poor bastard’s conflicted consciousness at any given moment. The technical audacity required in pulling this off may be the reason Two-Face was held back in the trailer. (via THE TWO PERFORMANCES OF TWO-FACE)