"Joe Strummer: The Future Is Unwritten" is a film for fans -- really big fans. More-casual admirers, perhaps those whose only Strummer CD is the Clash's "London Calling," should probably stay away.

You'd probably have to own (and enjoy) every cut of the vocalist's post-Clash catalog -- including all of the Mescaleros discs and his film soundtrack work -- for this exhaustively comprehensive documentary to hold your attention for the full duration. For everyone else, "The Future Is Unwritten" amounts to the cinematic equivalent of a two-hour-plus wait in the dentist's office.

The film comes courtesy of director Julien Temple, who is arguably the busiest man working in music documentaries. In the past, he's been at the helm of docs about Mick Jagger (1985's "Running Out of Luck"), the Sex Pistols (1979's "The Great Rock and Roll Swindle" and 1999's "The Filth and the Fury") and the famed British music festival Glastonbury (2006's "Glastonbury").

Given his first-hand knowledge of the '70s British punk scene -- which the Clash helped define -- one might think that Temple would be the perfect choice to handle a documentary about Strummer. Temple was one of the first people to actually film the Clash, long before the band members became heroes on MTV, and he maintained a long friendship with Strummer.

Yet, this is one case where familiarity has obviously worked against him. Temple knows his subject and he apparently expects the viewer to do his homework before venturing into the theater. It's all the little things -- like not identifying the people who speak on camera, as if the director's saying "real fans" should know these people -- that make this film feel so uninviting and will exclude many potential viewers.

That's a shame, since Strummer is certainly worthy of a documentary -- one that would educate the public as to why he's such an important figure in rock history. The crowd that will get this film, however, doesn't need educating. These people already understand how Strummer's poetic and political music with the Clash -- which, I'd argue, is the most significant body of work ever produced in the punk-rock genre -- changed the face of popular music.

The film is organized in a typically linear format, starting off with Strummer as a child and ending with his death from heart failure in 2002. The story is told through archival footage and new interviews with friends and admirers. Some of that old footage, especially of the Clash's early club days, is quite interesting, and a number of the interview segments are enjoyable. The latter, however, are blemished because many viewers won't know the identities of these talking heads or their relationships with Strummer.

Each chapter in the singer's life is treated with equal significance -- be it his childhood days or the years when the Clash was at its commercial peak. That might be Temple's way of saying that the Clash was only one part of what made Strummer so interesting.

That's true, to a degree, but it's also accurate to say that without the Clash, there would be no Joe Strummer film.

In all, some reorganization and a stronger focus on the Clash era would have made "The Future Is Unwritten" vastly more appealing to the general public. However, that apparently was not Temple's objective.

Reach Jim Harrington at jharrington@bayareanewsgroup.com.

'JOE STRUMMER: THE FUTURE IS UNWRITTEN'

C

Starring: Joe Strummer, the Clash

Rated: NR (Contains adult language, brief nudity)

Opens today: Shattuck, Berkeley; Lumiere, San Francisco

Running time: 2 hours, 5 minutes