Years ago, I saw something (probably on public tv) about Ingmar Bergman as a film director. It was footage of him directing a scene where one of his lovely actresses enters her apartment, to discover that her boyfriend has left her.
Bergman watches the rehearsal, and then directs this actress very explicitly and lucidly, and makes this simple "bit of business" go from ordinary to ... well, to Bergmanesque... weighty, important, vivid. It had to do with just how she drops her keys on a hall table, if I recall correctly, but it was extraordinary how well Bergman visualized and communicated the inner feeling that he was after.
I can't recall the name of the documentary or even the name of the feature from which this scene was taken, but I'd love to see this or another documentary on how Bergman directed actors.