Toronto 2012: 'Seven Psychopaths' Star Colin Farrell on the Differences in Acting for Theater, Film (Video)

Director Martin McDonagh also reveals to THR the challenges in moving from one medium to the other.

Even accomplished playwrights struggle with writing a film script sometimes.

So says playwright-filmmaker Martin McDonagh, who wrote and directed the crime comedy Seven Psychopaths, which stars Colin Farrell as a struggling screenwriter who inadvertently becomes entangled in the Los Angeles criminal underworld after his oddball friends (Sam Rockwell) and (Christopher Walken) kidnap a gangster’s (Woody Harrelson) beloved Shih Tzu.

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"It just took an awful lot longer to get my head around writing a script because it can go to so many different places in the course of a page whereas a play, eight pages, 10 pages of scenes is really just a course of conversations," McDonagh told The Hollywood Reporter in the THR TIFF Video Lounge at the Toronto International Film Festival.

Farrell -- who reunited with McDonagh, his In Bruges director, for Psychopaths -- adds that that there's also a big difference between acting in the theater and in film.

"I think film is a director's medium ... and theater is both a writer's and an actor's medium that's heavily influenced by a director's touch," he says. "But in film, you ideally trust your director and can give your director a lot of ... options. [In the theater] you can control your performance from start to end, you get to go on an arc ... and you get to reinvent each afternoon."

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As for how McDonagh's movies differ from other filmmakers, "his movies are more dialogue-driven," says Rockwell.

Seven Psychopaths hits theaters Oct. 12 via CBS Films.