Some actors would be terrified to play Butch Cassidy, a character forever tied to one of cinema’s last real icons, Paul Newman. But Sam Shepard, who plays an aging Butch in the new “Blackthorn,” which opened Friday, doesn’t seem in the least intimidated.

“That original movie, to me, was just two very charismatic, entertaining movie stars, having fun,” he explains one morning at a fashionable New York hotel. “It had nothing to do with authenticity or history. Butch Cassidy didn’t look anything like Paul Newman! He was a big, lantern-jawed, stout guy. Looked like a fullback.” No reason for Shepard not to give the part a spin, then, especially given the movie’s conceit — that the outlaws didn’t die in that 1908 shootout, and Cassidy wound up raising horses for decades in the Andes.

There are, however, shoes Shepard would refuse to step into. “I would never try Stanley Kowalski after Brando,” he laughs. “I mean, it’d be silly. Because it’s definitive. Nobody can do it as good.”

Marlon Brando, of course, starred in both the original Broadway “Streetcar” and its classic big-screen adaptation. But when it comes to his own plays, Shepard has given up hope of having them immortalized on the movies. “My plays can’t be adapted for film,” he says. “They’ve tried six or seven times, and it’s horrible!” When asked if that applies also to the one he starred in, 1985’s Robert Altman-directed “Fool for Love,” the author laughs. “Yeah!”

He believes in movies as a distinct art form, though, and wishes more people shared the sentiment. “I miss the days when film was considered in the same breath as painting or poetry, you know what I mean? This attitude of the ‘auteur’: Truffaut, all those people who would not only be the author but the director. It’s getting rarer and rarer; it’s all corporate.

“ ‘Transformers’? I mean, what the [expletive]?” he asks. “What has happened to film?”

Shepard accepts that he will never be one of those writer/director auteurs. Having tried directing twice, he says with a chuckle, “I realized I wasn’t really a filmmaker. It’s a very, very different instinct than theater. You have to be fascinated with the camera, and with the technology, and I’m not. I’m fascinated by actors, and audience, and theater predicament, but not with the camera.”

He’s generally given up writing for the movies, too, though he has enjoyed collaborating with German director Wim Wenders, whom he credits with being independent enough to guarantee scripts won’t be filtered through myriad meddling producers.

The better of those two films, “Paris, Texas,” revolves around a man who, like Butch Cassidy in “Blackthorn,” fled abruptly from his life, then found himself drawn back to it after others presumed him dead. Asked whether that’s an appealing scenario for an actor, Shepard pauses, and instead talks about what vanishing does for a writer:

“James Joyce said there are three ingredients to writing: silence, exile and cunning. Those are the three basic elements, he said, that a writer absolutely needs to write anything important. And the exile part of it — I mean, they all interest me, but the exile part of it really interests me. I’ve always felt that’s part and parcel of extraordinary stuff. Like ‘Don Quixote,’ you know, Cervantes. Beckett. There’s something in the exile part of it that has power, has force.”

That’s a question one assumes Shepard has little interest in. But any young actor out there should think twice about accepting the part of Sam Shepard. Some would say the definitive performance has already been given.