Watch: Natalie Portman spills the secrets of her performance in 'Black Swan'

It's funny that I'd be posting this only a few days after I've posted an interview with Jeff Bridges, because this is pretty much the polar opposite in terms of performances.

I'll admit it… I'm a tech nerd.  I love the way technology and performance are increasingly combined for an end result these days.  But I am also a huge fan of performances where an actor pushes themselves to a physical extreme in pursuit of a transformation that no computer could accomplish.

One of the defining performances I saw as a young film fan growing up was Robert De Niro's in "Raging Bull."  I studied that film, looking at the way De Niro took himself from lean, polished, chiseled physical perfection to this bloated, ruined bag of fat, and it stuck with me because I couldn't imagine that being the same person.  Since then, we've seen other actors who have pushed themselves to extremes in order to create striking images and give life to stunning characters. 

Christian Bale practically built his early career on his ability to waste away to almost nothing, and if you saw Matt Damon in one of his early roles in "Courage Under Fire," what he did to himself in the film actually hurt him.  One of the reasons I would consider Michael Fassbender one of the most promising actors to emerge in the last few years is because of his harrowing work in "Hunger."  It's dangerous to push your body to extremes in either direction, which is one of the reasons we can't look away when we're watching it.

With "Black Swan," Natalie Portman had to learn to do something convincingly on camera that people train their whole lives to do, and even with the training she had in childhood, she still ended up pushing herself further than I think she bargained for, training for a full year for the film.  There were doubles used, of course, and even some sly tech tricks that I'm sure they'll reveal more fully on the eventual Blu-ray, but Portman still had to sell it and make you believe she does the dancing, whether she really does or not.  We discussed that and many other things when we sat down for this extended interview at the W Hotel in Hollywood a few weekends ago.

In person, Portman is stunning, which is to be expected, but before we rolled the cameras, I was struck by just how funny and sharp she was.  I'm excited to see her show up in the positively deranged "Your Highness" next year, and we talk about that a bit too in the interview.

"Black Swan" is now playing in limited release and will roll out in more cities throughout the month.