Banksy, the pseudonymous British street artist, has built his reputation on stunts - like inserting his own work among the masters’ in museums - that taunted the market in which his pieces sold for millions. But with his latest project, the documentary “Exit Through the Gift Shop,” he is laboring to convince audiences that he’s playing it straight.

The film follows Thierry Guetta, an amiable Frenchman who lives in Los Angeles and videotapes everything - or so we’re told. When Mr. Guetta and camera eventually tunnel into the world of street art, capturing that scene’s luminaries, like Shepard Fairey and Swoon, working on rooftops and in alleys under cover of night.

It seems to be a natural fit for a documentary. But Mr. Guetta’s footage turns out to be largely unwatchable. “He was maybe just somebody with mental problems who happened to have a camera,” Banksy says in the film.

So Banksy decides to take control of the material himself - or so we’re told. Mr. Guetta, meanwhile, morphs into a street artist, staging an opening exhibition in Los Angeles that turns him into an overnight sensation, all of which is captured in “Exit Through the Gift Shop.”

The film itself was a sensation at the Sundance Film Festival this year . At the Berlin International Film Festival in February, Banksy called a news conference, only to cancel it at the last minute and show a video, in which he appears in shadows, cloaked in a hoodie and with his voice disguised, as he does in the film, to vouch for its veracity.

The thing is, both Banksy and Mr. Guetta are pretty unreliable narrators. The immediate rumor was that Mr. Guetta either didn’t exist at all, that he was working secretly with Banksy or that he was Banksy himself.

But everyone involved has vouched for it. “Of course the more I try to say it’s all true, the more it sounds like I’m somehow perpetuating the conspiracy,” said Mr. Fairey, a friend of Banksy’s.

Mr. Guetta did not respond to a request for comment ? though he does seem to exist and to be as idiosyncratic as he is in the film.

“I don’t know why so many people have been fooled into thinking this film is fake,” Banksy, or someone purporting to be he, wrote in an e-mail message . “It’s a true story from real footage. Does it bother me people don’t believe it? I could never have written a script this funny.”

Ultimately, wondering whether “Exit Through the Gift Shop” is real may be moot. It asks real questions: about what it means to be a superstar in a subculture built on shunning the mainstream; about how that culture judges, and monetizes, talent.


By MELINA RYZIK


PARANOID PICTURES
Banksy, famous for his pranks, as he appears in ‘‘Exit Through the Gift Shop.” He insists the film is real.