It was a year ago that Christian Bale was the world's biggest comic book hero in "The Dark Knight." It was only a month ago that he was humanity's savior in "Terminator: Salvation." 

In "Public Enemies," though, Bale takes on a greater challenge: Supporting player. 

Opening this Wednesday (July 1), "Public Enemies" focuses on the FBI's efforts to bring down notorious gangster John Dillinger in the heart of the Great Depression. While Bale's Melvin Purvis is probably the hero, the actor knows that in Michael Mann's gangster film, audiences are coming to root for the doomed gangster especially Dillinger is played by Johnny Depp.

"It's the story of Dillinger," Bale tells reporters without hesitation. "I"m just a piece of that puzzle."

Speaking to journalists at the "Public Enemies" junket, Bale's passionate research into the period and into his character are clear, especially the time he spent with Purvis' son.

"We spent a great deal of time together. He was very reach outable. I went down to their hometown and met with remaining family and friends," Bale says. "He's written a wonderful book called 'The Vendetta' which is focused on Purvis' relationship with Hoover which is really how I approached this entire role. I never viewed Purvis as having a real personal zeal for taking down Dillinger. I think that he was somebody who was very understanding in acknowledging why the public felt Dillinger to be almost a hero. He wasn't unaware of the problems of the day and the terrible deprivation of the majority of the population. He had a personal hatred for Baby Face Nelson because Nelson had killed Barton and then Baum who Purvis brought with him, who were very close friends of him. But otherwise his driving motivation was that he truly believed in Hoover and had a great desire to realize Hoover's brilliant vision. That's really what I played with in my mind throughout this movie was the conflict between wanting to achieve that vision but recognizing Hoover's own compromises which Purvis wasn't entirely happy with making."

Bale's own distaste for artistic compromises is well known and he found a fellow traveler in Michael Mann.

"I felt nothing but kinship in terms of devotion to the work and found it to be incredibly inspiring and it's very satisfying to work with somebody who has that level of commitment and immersion and genuine passion for directing rather than for being a director," Bale enthuses. "There is a huge difference. It's the same in acting. A lot of people, they love being an actor but they're not so keen on acting."

One thing that Mann brought to "Public Enemies" that added to Bale's experience was the director's familiar commitment to shooting in digital, giving the actor his first prolonged exposure to the shooting style.

"I found it a real eye-opener. I'd never worked with HD before. I wish I could work with it on every movie now," the new convert says. "Not only does it give great freedom in terms of the length of take and the numbers of takes you can have, you can shoot for 52 minutes straight rather than the usual six minutes. So much more like life. You don't have to stop and pause and think too much about what you're doing. You can really feel like you're living it much more. There were such extraordinary talented camera operators and Dante being the DP and Michael, he would operate at times as well. They had such incredible speed, I could just run at them knowing that within one inch, they would certainly have the camera out of my face and I wouldn't be knocking them down. Michael would encourage me anyway, 'Hey Christian, knock them down if they're too slow.'"

Bale adds, "Also the style in which it was shot was fantastic for someone like me who I don't tend to want to know if my close-up is being done or if it's a wide shot, I don't really feel like I need to know that. We often shot masters and close-ups at the same time. I enjoyed that greatly. If anybody ever listens to me, I would be strongly endorsing using HD in future movies."

The "Newsies" veteran also endorses period weaponry, or at least he took pleasure in kicking it Depression Era after battling killer robots with the latest in imaginary future munitions. 

"I think the guns as well of that time were sort of the last of the characterful guns," says Bale of the "quaint" firearms used in "Public Enemies." "The Thompson still had so much wood on it. It still kind of smells good after you fire it. You do feel almost an affection towards the weapon. The modern day weapon is far more capable and lethal but in my mind lack that character that the weapons seemed to have back then, as did the cars as well and the suits and everything. It was such a Golden Era."

The Golden Era begins for viewers on Wednesday when "Public Enemies" hits theaters.