Darren Aronofsky "scares" a lot of A-list actors by being so demanding.
The 41-year-old filmmaker - who has directed stars including Mickey Rourke ('The Wrestler') and Hugh Jackman ('The Fountain') - believes he is "direct to a fault" with many people in his films, but found Natalie Portman in psychological ballet drama 'Black Swan' to be among the hardest workers he has come into contact with.
He said: "I'm very direct, probably direct to a fault with actors, and I've probably scared away a lot of A-list actors, because I tell them how much of a pain this process is going to be, how difficult it is.
"Natalie's worked harder for me than anyone, and that's because of the dance. It's an unbelievable accomplishment, what she's done, physically. The fact that 90 per cent of the dancing on the screen is here. That is unbelievable."
Darren - who is widely tipped for success at The Oscars thanks to 'Black Swan' - also has strong views on people method acting in Hollywood movies because it is nothing like theatre work and can be "pretty selfish".
Discussing the idea that 'Black Swan' is a critique of the technique - used by actors including Meryl Streep and Vanessa Redgrave in the past - he told movie website Den of Geek: "I think it's actually pretty selfish. It's just make-believe.
"Film is basically little bursts of acting. Twenty seconds here, 10 seconds there. Two seconds there. I mean, sure, in between takes you could stay there, but once the take's over, when you're in the make-up chair, come on.
"To me, it' doesn't impress me, actors that do that."