Armie Hammer pushed to his limits playing twins in Social Network

Armie Hammer struggled to play the Winklevoss twins in The Social Network because director David Fincher pushed the actor to his limits on the "technical shoot."

The star had no idea he would be playing both Tyler and Cameron Winklevoss in the movie about the evolution of the social networking site - and Fincher insisted on absolute perfection from the 25-year-old's dual performance.

Hammer tells Prestige magazine, "When we signed on, I didn't know I would be doing both. I thought, 'Oh great, I got hired for one of the twins.' And then, about a week into production, Fincher called and said, 'You're going to do both of them.' But it was difficult.

"It was much more of a technical shoot then anything else I've experienced. You're always told in acting school that it's about the emotion and the truth and all that stuff. But with this, it was more like tilt your head a little more to the left or look over here at this tennis ball. I would start as Cameron Winklevoss and we would shoot the scene until Fincher was happy, which would probably be 40 or 50 takes.

"Then he would say 'switch' and I would go and take off the Cameron outfit, take off the make-up, the hair and all that, and get redone as Tyler Winklevoss, remember the character of Tyler and get into that. They would put a tennis ball on a stand or a piece of tape on the wall and say, 'Okay, there's your brother.'

"There were definitely some nights, when we were working late, when Fincher would say, 'You're letting the brothers bleed together. Remember what we're doing.' And I'm like, 'It's four in the morning and we've been doing this for 18 hours and we're on take number 1,200. Give me a break, man!'"

The Winklevosses became embroiled in a legal dispute with Facebook founder Mark Zuckerberg over allegations he used their ideas for a social networking site they were developing at Harvard University in 2003.

The legal battle inspired the 2010 movie.