Believe who you want on this one. My bet is on the double, Sarah Lane. Having just watched the film last night, I wondered how much of the dancing Portman could have actually done. My intuitive answer was "not much." Maybe yes, then again according to Black Swan” dancer – choreographer Benjamin Millepied, who is expecting a child with Portman, maybe no. (see Wall Street Journal excerpt at bottom of post)
This from Entertainment Weekly:
"The ballerina who served as a dancing double for Natalie Portman’s Oscar-winnning role in Black Swan tells EW she has been the victim of a “cover-up” to mislead the public about how much dancing Portman actually did in the film. “Of the full body shots, I would say 5 percent are Natalie,” says Sarah Lane, 27, an American Ballet Theatre soloist who performed many of the film’s complicated dance sequences, allowing Portman’s face to be digitally grafted onto her body."
.... and this from a Wall Street Journal story:
"“Black Swan” dancer/choreographer Benjamin Millepied, who is expecting a child with Portman, told the Los Angeles Times this week “Honestly, 85% of that movie is Natalie.” (Lane says that if she had to quantify it, Portman did “about 5%” of the on-screen dancing.)"