Leonardo DiCaprio says working with Martin Scorsese is like being at school.
The 'Departed' actor - who has just completed work on 'Shutter Island', his fourth movie with the director - and his co-stars are always requested to watch a vast number of films before working on a new project because the filmmaker is so insistent on thorough research.
He explained: "It's like a little cool learning workshop before we start to make the movie. It's a film course, you get a crash course, like an education.
"He's the best teacher. I'm sure that there are professors out there but I would challenge anyone to know as much about movies as him.
"I would see Marty up there against anyone in the world as far as film knowledge is concerned because it's weird. He knows not only the film but the editor and second assistant director of an obscure French film. It's weird because that's what he does, that's all he does, that's who he is.
He's a man of film."
The director's research is so thorough, his choice of research viewing does not just include other movies of a similar genre to the one he is making.
Leonardo added to Total Film magazine: "We watch a lot of films for lighting and mood tone, a lot of obscure movies.
"I remember for 'The Aviator' we watched 'House of Wax' just for the dialogue - because Marty remembered the dialogue in that movie was really snappy."