Ben Affleck hopes Batman fans who were skeptical of him playing the caped crusader in Batman v Superman: Dawn of Justice realize how seriously he took the role.

"The most difficult thing about making this movie, honestly, was the physical aspect," Affleck told The Associated Press on Sunday on the red carpet for the film's New York premiere at Radio City Music Hall.

Affleck said he wanted to be in shape, so he worked out hard.

APTOPIX China Batman V Superman

'Fans have come to expect that if you're going to play a superhero, you got to look in the body like a superhero,' Ben Affleck, seen in Beijing earlier this month, said of his gruelling physical preparations for Batman v superman: Dawn of Justice. (Ng Han Guan/Associated Press)

"Having to be in the gym every day, six in the morning ... I wasn't used to that kind of workout regimen," Affleck said.

Fans have come to expect that if you're going to play a superhero, you got to look in the body like a superhero. I knew the camera was going to be looking at me and the guillotine was there so I knew I had to be ready."

Answering the backlash: 'I just wanted to do my best'

When Warner Bros. made the announcement nearly three years ago that Affleck would play Batman, some fans weren't thrilled, and the backlash led to petitions asking the studio to remove him.

Eventually, it blew over, and the two-time Oscar winner feels proud to be part of the Batman legacy.

"I'm really honoured to be part of a tradition that Christian Bale and Christopher Nolan, great talents, worked on. Michael Keaton, Val Kilmer, George Clooney, Tim Burton, great talents. So I just wanted to do my best. I think we did something different, but something that is still very much Batman," Affleck said.

NY Premiere of Batman v Superman: Dawn of Justice

Amy Adams reprises her role as Lois Lane in Batman v Superman: Dawn of Justice. (Charles Sykes/Invision/Associated Press)

Co-star Jesse Eisenberg shared a similar experience when he was cast as Superman's arch-nemesis, Lex Luthor.

Eisenberg, famous for his role as Mark Zuckerberg in The Social Network, empathized with his critics.

"I can assure them as critical as they are of me, I'm more critical. No one is more concerned or critical or worried about doing a good job than I am," Eisenberg said.

Amy Adams, who plays Lois Lane in the film, praised both Eisenberg and Affleck.

"I think the audience is going to have to decide for themselves. [I] got to see it, and I was blown away," Adams said.

"They both bring something we've never seen before in these characters, but something that really pays homage to the canon, so I think they are going to be really happy."

"I think people are going to like it," Affleck said. "All you can do is do your best."