During the filming of Pandora’s Box, [G.W. Pabst] asked Louise Brooks, as Lulu, just emerged from taking a shower and coming into the living room to greet her lover, Alva (portrayed by Franz Lederer), “What do you have on under that robe?”
“My slip,” answered Miss Brooks.
“Go back in the bathroom and take it off,” said Pabst, which she did.
When she returned, wearing just the robe, she asked her director, “Mr. Pabst, why did you make me take my slip off? The audience won’t know that I have nothing on under my bathrobe.”
“That’s right,” he replied. “The audience won’t know, but he’ll know,” he said, pointing at Lederer, “and he’ll play the scene with you differently, knowing that, than he would if he didn’t know it. And that’s what I want, that difference.”
Miss Brooks told me this story and I think it underlines the point I’m trying to make that the director must do everything he can think of to feel that the scene is ready to be played to the maximum that he can feel. If he feels it, the audience will feel it. Ergo – the director as psychologist.”
-Herman G. Weinberg, excerpted from The Complete Wedding March (1975)