An impressionistic look at a rock icon

''Dream of Life'' follows Patti Smith at home, on the road, and in performance.

It took 11 years to shoot "Patti Smith: Dream of Life," and at times you may feel like the movie's playing in real time. Impressionistic, inspired, dull, eccentric, raucous, meditative, profound, pretentious - this isn't a portrait of the life of the high priestess of punk so much as a steeping in it. As such, it's for dedicated fans; newbies are hereby directed to Wikipedia and a CD of 1975's landmark album "Horses," still jaw-dropping after all these years.

Directed by art and fashion photographer Steven Sebring, "Dream of Life" captures Smith in the aftermath of a time of intense loss. Having suffered the deaths of her husband, MC5 guitarist Fred "Sonic" Smith, her brother Todd, and pianist Richard Sohl in the early '90s, the rock icon emerged from a long period of domesticity and mourning, creative fires restoked.

The albums and concerts of the past decade have seen Smith urging a new generation to recapture the stalled zeal of the punks and change the world; her profane high-decibel reading of The Who's "My Generation" now takes time to furiously inveigh against George W. Bush. Currently 62 and carrying herself with the bearing of a shamaness, she's well on her way to becoming the Georgia O'Keeffe of rock: committed, serene, indestructible.

"Dream of Life," unfortunately, meanders in and out of focus, sometimes fatally. Sebring tags along with the artist during her global travels (Rome, Paris, Japan, Israel) and sits backstage as she jokes with family and friends (musicians like Flea and REM's Michael Stipe appear fleetingly). We see her two children, son Jackson and daughter Jesse, in various stages of adolescence and early adulthood. In one thoroughly charming scene, she drops in on her parents' unprepossessing New Jersey home, kvelling over her father's coffee and listening indulgently as he gripes how deaf her concerts have made him.

Sebring constantly returns to Smith's bedroom as the musician rifles through her past, and these scenes can be both poignant and enervating. When she talks of Robert Mapplethorpe, the late photographer and her closest New York friend, the emotions run close to the surface. A guitar-strumming reunion between Smith and playwright Sam Shepard is perfectly charming - long-ago lovers, they have the matching tattoos to prove it. ("That was a weird night, wasn't it?" Shepard muses.)

But then we get a long sequence of Smith playing with her cat, and you realize Sebring's eye for an image and a moment doesn't extend to a larger statement or even a consistent scene. (Nor, most frustratingly, to nearly enough footage of Smith in performance.) When it works, this approach honors the artist's debt to the Beats, Bob Dylan, and France's Decadent movement - the radical "disordering of the senses" sought by poet Arthur Rimbaud. When it doesn't work, which is all too often, "Dream of Life" goes slack.

It takes a very specific talent - a genius, really - to let it all hang out in a way that possesses real shape and force. Smith has it; Sebring doesn't. (In his defense, neither do most of us.) "Dream of Life" is a fond snapshot of rock's Mother Courage that proves, among other things, the limitations of fondness.

Ty Burr can be reached at tburr@globe.com. For more on movies, go to www.boston.com/movienation.