There's a striking sequence in "I'm Not There," Todd Haynes' new Bob Dylan movie, in which Dylan's besieged mid-'60s artistic transformation is set within the surreal glare of the spa scenes in Fellini's "8 1/2," in which a desperate film director attempted to work out his own artistic confusion. This is a perfect imaginative combination of pop-music myth and cinematic iconography, and it resonates memorably. The movie has been made with great affection for its subject, but it has some sharp edges, too; and there are two remarkable performances in it that are worth seeing.

For the most part, though, sitting through this unusual-but-not-a-lot-more-than-that picture, in which six different actors impersonate Dylan in various phases of his career, is like contemplating a package that's arrived in the mail containing something you never ordered and can't imagine why anyone else would, either. The notion that Dylan's various public personas — as opposed to his music — merit earnest contemplation at this late date seems silly. And yet here they are, on pointless parade: the whey-faced young folksinger Bob; the sharecropper-serenading protest Bob; the turned-on, meet-the-Beatles Bob; and of course the Woodstock Bob of The Basement Tapes. Actually, I suppose these multi-Dylans are thought-provoking, in a way. I kept wondering, "Why?"

There's no particularly compelling story here, apart from the familiar chronology of Dylan's career, and there's no character development apart from the obvious one of a succession of actors playing the same main character. There are only those half-dozen Dylans, wandering in a field of evocative visual cues: the doomed motorcycle ride; the Big Pink and — yikes! — "Renaldo and Clara" references; and for the Dylan fetishists who will most truly groove on this movie, more oblique touches like a Gorgeous George flyer, a visual nod to the cover of the "Freewheelin' " album, a glimpse of a faux Moondog rising up in his robes on the streets of Manhattan, and Pete Seeger and Albert Grossman look-alikes wrestling for control of the amplification system during the Dylan-goes-electric contretemps at the 1965 Newport Folk Festival.

The best of the Dylans are Cate Blanchett and Marcus Carl Franklin, not necessarily in that order. Franklin plays the larval Dylan, fresh out of Minnesota, fired up by the songs of Woody Guthrie, and spouting playful lies about his train-hopping hobo adventures. This Dylan is an 11-year-old black kid, which is a bold idea, and Franklin embraces it with startling confidence. He's irresistibly winning; and when he strums up a version of "When the Ship Comes In," surrounded by a doting white family in a suburban living room, he's a knockout.

Blanchett brings her extraordinary powers of character penetration to the sour, mid-'60s hipster Dylan familiar from D.A. Pennebaker's 1967 tour documentary, "Don't Look Back." With her skinny suits and wild, plugged-in hair, she gets the character's speed-fueled hostility just right. But there's no point at which you're not aware that this is a woman portraying a man, despite the expertise with which Blanchett pulls it off; and since she occupies a central place in the film, the imposture goes on too long and eventually settles into the shape of a stunt, which, basically, is what it is.

The other Dylans in the film are nowhere near as interesting — although Ben Wisham brings a droll snap to his brief appearances as a sort of Rimbaud-Bob. Both Heath Ledger, as the love-man Bob, fretting his way through a collapsing marriage, and Christian Bale, as Bob the Protester (and later the born-again evangelizer), are too physically substantial and movie-star-handsome: their un-Bobness is distracting. Most dismal of all is the extended allusion at the end of the picture to Sam Peckinpah's "Pat Garrett & Billy the Kid," the 1973 movie in which Dylan made his first appearance as an actor (and to the soundtrack of which he contributed the transcendent "Knockin' on Heaven's Door"). Here the Dylan role is taken on by Richard Gere, of all people, and the rambling storyline shuffles past the point of tedium into a complete shambles. (It's also unfortunate that Julianne Moore was cast as the Joan Baez figure in the film — is there anyone less like that bracingly tart woman?)

Because Haynes and his famed cinematographer, Edward Lachman, are so committed to the movie's odd concept, the picture has some value as a well-crafted curio. For most of its length, though, it's merely curious — a different and too-often tiresome thing.

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