Robert Redford has revealed he was drawn to Captain America: The Winter Soldier because he wanted to work on a "high technology" film.
The two-time Oscar winner will play a senior leader at S.H.I.E.L.D. in the movie, his first superhero film, and told Entertainment Weekly he signed up because he wanted to try something a bit different.
"One of the reasons that I did it was I wanted to experience this new form of filmmaking that's taken over where you have kind of cartoon characters brought to life through high technology," said the 77-year-old.
"The Avengers series is a product of high technology playing a major role in the new order of filmmaking so I wanted to experience that - I just wanted to know what that was like and I had that opportunity, so for me it was like stepping into new terrain just to experience what it was like."
It is due to be released in April.