Lexington's Sally Mann, anointed "America's best photographer" by Time Magazine in 2001, is about to become a star of the silver screen as well.

"What Remains," a documentary of Mann's life and work by New York filmmaker Steven Cantor, will be shown at this year's Sundance Film Festival, to be held at Park City, Utah, Jan. 19-29. The festival, whose Web site calls it "The premier U.S. showcase for American and international independent film," is a program of the Sundance Institute, founded in the mountains of Utah by actor Robert Redford in 1981.

Cantor began filming Mann in the early '90s, as her edgy photographs of her sometimes-naked children were making her famous. "Immediate Family," title of a traveling exhibit and 1992 photo book, cemented Mann's international reputation and reportedly made her a millionaire. It also led some viewers to question her upbringing and her morals.

Cantor said he has continued to document Mann's work in part because she is articulate about it -- something that could not be said of every artist. "She is so conscious of what's she's trying to do," he said.

Cantor's 1993 short film, "Blood Ties: The Life and Work of Sally Mann," was also shown at Sundance.

"I was 22 years old and didn't know what I was doing," Cantor says now of that early effort. "Blood Ties," he said, focused too much on the controversy surrounding Mann at the time and not enough on the art.

No one could say that about the new, feature-length documentary. It follows Mann from the early '90s, when she was still taking photos of her young children, through a period spent photographing Southern landscapes to a later focus on death and bodily decay.

At one point, the filmmakers follow Mann to a research farm in Tennessee, where human bodies are left lying about to decay naturally.

"I love mummified skin," Mann says, in one of the film's more interesting moments, between camera shots of her peering at swarms of maggots and caressing a shriveled human foot. "The way it undulates and moves. It seems alive."

We also see Mann displaying and photographing the bones of a long-dead family pet.

Along the way, we learn about her husband Larry's long battle with muscular dystrophy; about her now-grown daughter Jessie's modeling fixation ("I'm like this needy modeling junkie. I love it"), and, from Mann's mother, that for the first two years of her life, little Sally refused to wear any clothes.

Cantor sent Mann -- who can be a bear about her privacy -- rough cuts of his work-in-progress, and agreed to "tweak" numerous things in the final take, he said. On the other hand, "I think she to a large extent trusts me," Cantor said -- which might explain some of the film's most revealing footage. At times Mann's eyes dart from side to side, as though she wishes to escape the camera. And she breaks into tears the day a New York gallery cancels "What Remains," her exhibit of photographs of decaying bodies (which also gives the film its title). The scene is painful to watch, as we see Mann veer from resignation to lacerating self-doubt.

"You all ought to pack up and go home," she says, jokingly, to the unseen film crew, implying that she is a has-been. And then, starting to sob: "It's humiliating. It's embarrassing ... You lose confidence. I think it's important, but maybe it isn't. Maybe it's four years of wasted time."

The episode has a happy ending, as the prestigious Corcoran Gallery of Art in Washington, D.C., exhibits the photographs instead.

It's also clear from the film that Mann licks her wounds in comfort, surrounded by family, horses and dogs on her postcard-pretty Rockbridge County farm. Still, the crying scene is a window, not just on the artist's personality and sensitivity, but the fragility of success and the strangeness of art.

And what does Mann think about it all? She admits to some uneasiness at being the subject of a movie -- but also says she is "extremely flattered" by all the fuss.

"There are sections that I cringe through when I watch them," Mann said in an e-mail. "But before we started, I made a promise to myself not to let vanity interfere with the truth of this story. I never did anything to prepare for the film crew, just wore my usual clothes, let my hair do its usual tangly gray thing, no makeup and no big words."

She hopes the film, with its emphasis on her workaday world, will both deflate unrealistic notions about artists and their glamorous lives and convince youngsters that " if she can do it, I surely can, too."

Mann and her three now-grown children, Jessie, Emmett and Virginia, plan to attend Sundance, where the film debuts Jan. 21. Husband Larry "has to stay home and stoke the wood stoves," Mann said.

"What Remains" is in the American Spectrum category, which includes documentaries with an American angle to them, Cantor said. He said the film will appear on HBO sometime in late 2006 or 2007. It will also be available on DVD.

In the meantime, Mann may want to keep a bag packed.

"Sundance tends to be the springboard for every other film festival in the world," Cantor said. "We'll probably do a worldwide tour."