We live in a golden era for non-fiction films. Spellbound, Super Size Me and Michael Moore’s socio-political broadsides break box-office records. March of the Penguins, a French documentary, emerged triumphant during a summer of blockbuster flops.

Keeping it real is the watchword, industry insiders insist. And it’s a view endorsed by the banquet of true stories on offer at a double bill of UK film festivals opening this week.

The London-based independent film showcase Raindance includes both fiction and nonfiction stories, but the latter dominate this year. Hard on its heels (and sharing some of the same films) comes the 12th Sheffield International Documentary Festival. Here you will find not just documentaries on offer but rockumentaries, shockumentaries and even mockumentaries.

Musical stories are well represented. The fashion photographer David LaChapelle’s Rize, which celebrates LA’s hyperkinetic “clown dancing” scene, makes its UK debut in Sheffield. And both festivals will show Jeff Feuerzeig’s acclaimed rock-doc The Devil and Daniel Johnston, as well as Punk: Attitude, an ambitious history of punk from Don Letts.

The Sheffield line-up also includes Moore-style polemics led by Alex Gibney’s darkly funny Enron post-mortem The Smartest Guys in the Room. But the prevailing trend is for folksy snapshots of backwoods Americana in the feelgood spirit of Spellbound. Among those showing in Sheffield are Standard of Perfection: Show Cattle, directed by Mark Lewis, and Pucker Up: The Fine Art of Whistling, by Kate Davis and David Heilbroner. Both have already been bought by the BBC.

After years of making Emmy-winning documentaries about torture and child abuse, Davis says she was drawn to her whimsical theme for light relief.

“Whistling appealed to me because it seemed both ludicrous and also potentially soulful,” she says. “I took it as a bit of a challenge to try and tread that line. It became a metaphor for life, of how we forget to look within and find simple pleasures.

The same could be said of Rick Minnich’s Homemade Hillbilly Jam, a portrait of dying musical traditions in rural Missouri, which also makes its UK debut in Sheffield. The third feature-length documentary by the US-born, Berlin-based director is another quirky insight into an America that most Americans would barely recognise.

“It’s a culture that is fading but putting up a good fight,” Minnich says. “Maybe there is more of a movement of people finding these subcultures within their own culture. The response in North America to Homemade Hillbilly Jam has been, ‘Wow, are there still people like that?’ They don’t necessarily want to live that way, but they are glad that way of life exists.”

But is this brave new world of DIY documentaries a wholly positive move? While cheaper equipment and growing audience appetite has fuelled a boom in nonfiction films, many directors privately question the creative and financial benefits.

“The exciting thing is that the public will now go and see documentaries, which was not the case ten years ago,” Davis concedes. “From the buyer's point of view, it could feel like a golden age. But for film-makers there is only one Spellbound, only one Bowling for Columbine. It’s still a daunting prospect trying to get your film seen.”

Letts agrees: “The boom is in Michael Moore films, but for the rest of us it’s a labour of love. The more interesting ideas are left of centre, so you’re always going to have a struggle with that. And the downside of affordable technology is mediocrity. Just because you can afford it doesn’t mean you can do it.”

Raindance runs until Oct 9, www.raindance.co.uk; the Sheffield International Documentary Festival, Oct 10-16, www.sidf.co.uk

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