Amanda Seyfried watched 'Deep Throat' to prepare for her role in 'Lovelace'.

The 27-year-old actress portrays famous 1970s porn star Linda Lovelace - real name Linda Boreman - in the 2013 biographical film and she admits she viewed the X-rated classic from 1973 to research her part.

Speaking at the premiere of the movie in New York City on Tuesday night (30.07.13), Amanda admitted: ''Before shooting I saw the original film. Online, or DVD I can't remember.''

Amanda also revealed she wanted to impress her co-star Sharon Stone - who was cast as Linda's mother Dorothy Boreman - because she was nervous about working with one of her screen idols.

Amanda added to the New York Post newspaper: ''Our beginning was difficult because I was nervous about fabulous Sharon Stone. I wanted to be good for her. And she was so helpful. She slapped me into the role. She was really maternal.''

The young actress was joined at the premiere by Sharon and her co-stars Peter Sarsgaard, Hank Azaria and Chris Noth.

Unlike Amanda, Sharon, 55, didn't feel the need to watch 'Deep Throat' to prepare for the film and she claims she's never watched a pornographic movie.

The 'Basic Instinct' star said: ''I never saw the original film. Never saw a porno.''