Considering how much time we all spend marvelling at the fruits of their craft, it's surprising how little public recognition cinematographers get. Even the most hardened film buff probably couldn't tell you who shot Titanic, even though it won an Oscar for Best Cinematography. (It was Russell Carpenter, by the way.)

But one name hard to avoid at this year's Edinburgh Film Festival is that of Seamus McGarvey, the young Northern Irish cinematographer who has no fewer than three features playing at the festival this weekend. Beyond their low-budget British origins, it would be hard to imagine a more diverse trio: The War Zone, Tim Roth's gruelling account of incest in a middle-class home; I Could Read the Sky, a poetic, non-narrative exploration of memory; and The Big Tease, a hilarious Spinal Tap-esque "mocumentary" about a Scottish hairdresser's misadventures in Los Angeles.

From the shadowy interiors and glowering West Country skies of The War Zone to the sunlit West-Coast kitsch of The Big Tease, the films couldn't look more different either. But then for McGarvey, the job of the cinematographer - or DP (director of photography) as they're known in the industry - isn't about imposing a style or look, but "embellishing the script with the camera, finding the photographic heart of a script". On The War Zone, adapted from Alexander Stuart's controversial novel about a home torn apart by incest, Tim Roth originally wanted a frenetic feel, with lots of dynamic Steadicam movement. But in collaboration with McGarvey, he ultimately opted for a much more austere, spartan approach. "It becomes more like a visual testament," McGarvey explains, "like photographic evidence of what's going on in the home. The subject-matter requires that integrity."

The light was obviously a factor. "When we're shooting exterior here in Britain," McGarvey sighs, "a lot of what we do is damage limitation." Over the years, perhaps of necessity, he has turned into something of a bad-weather specialist. The road movie, Butterfly Kiss, for instance, was shot on and around the motorways of Lancashire. "It was horribly dull and grey and morose," McGarvey remembers. "But that quality really shows in the film. It becomes a look in itself." On 1997's The Winter Guest, set in a Scottish town so cold that the sea has frozen over, McGarvey did wonders with a restricted palette of greys - rocky beaches, frosty fields, stone houses, relentlessly cloudy skies - to turn what was at heart a filmed play into one of the most visually beautiful British films in recent memory. (Along the way, he made an unexpected beauty out of Emma Thompson, too.) As for The War Zone, shot in wintry Devon, McGarvey decided to make a virtue of the gloom, to the point where he found himself actively having to avoid sunlight on occasion in order to stay true to the film's sombre aesthetic.

Given the enormous time delay built into the whole process of film production and distribution, the film's screening at Edinburgh are already ancient history for McGarvey, who in the meantime has graduated to bigger projects across the Atlantic.

His agent has recently been receiving inquiries from the likes of Kathryn Bigelow and Steven Spielberg. ("Spielberg was one to tell my mum," McGarvey laughs. "It's the first time I've mentioned anybody she's heard of. She keeps going on at me to get a proper job, shooting the news for the BBC.")

Following a stint in Canada photographing Julianne Moore, Sigourney Weaver and Andie MacDowell in the $20m drama A Map of the World, McGarvey hit the big time earlier this year when Stephen Frears picked him to shoot High Fidelity, Nick Hornby's saga of north London record shops, now somewhat bizarrely transplanted to Chicago, with an all-star cast including John Cusack, Tim Robbins and Catherine Zeta Jones.

"Because [High Fidelity] is a film about people younger than I am," Frears explains on the phone from the Dorset cutting room where he's holed up editing the film, "I thought I ought to have younger people around me to tell me how young people behave, so I was looking for a young cameraman. A couple of people had talked about [Seamus] with tremendous excitement. So I met him, and he seemed so fresh and to have such vitality and imagination.

"There was a brief moment when I thought, `This boy is so young I can't throw him to the Hollywood wolves' - and then he got the job."

Frears isn't joking when he talks about the "Hollywood wolves". McGarvey may have handled the leap to managing a 20-strong Hollywood crew, but his innovative style on High Fidelity caused a few ructions at Disney, never the most adventurous of studios. "It was terrifying," recalls McGarvey, in the flesh not quite the "boy" Frears promised, but still a youthful 32. "I was trying to do stuff visually that was pushing the boat out a little bit in terms of contrast and colour - that's why Frears got me on board, because he wanted something different; he didn't want it to look like Dangerous Liaisons. But when the powers that be in LA saw the first rushes, they thought that it was too extreme and they freaked out. I thought I was going to get fired."

Luckily, with the support of Frears and Cusack, who was also one of the producers, McGarvey was able to win the studio round. "Once everything settled down," Frears comments, "it became apparent he was lighting it the right way. Because it's not the kind of film Disney usually make - I don't mean by that that it's shocking or pornographic or anything, it's simply because it's about modern life - I think they weren't used to seeing footage as realistic as we'd shot."

At the end of the shoot, Disney's head of production arrived on set and personally congratulated McGarvey, but the experience was still an eye- opener for the young DP. "I was under terrific scrutiny the whole way," he explains. "That pressure was something that I really wasn't used to. I come from a low-budget tradition; I'm used to working in a more familial structure, with producers who have a real sense of we're all in this together, something which simply doesn't exist in the dog-eat-dog world of Hollywood movies."

If any further demonstration of his versatility were required, McGarvey will also be staging a special one-off event in the film festival delegates' centre on Saturday, when - with the promised assistance of John Cusack as barman - he will be demonstrating the making of the perfect Martini described by Luis Bunuel in his autobiography My Last Breath. "Bunuel specified that the afternoon sunlight should shine in a shaft through the vermouth as it drops into the glass," McGarvey explains. "So we've got a big Xenon spotlight and we're going to recreate the Barcelona afternoon sunlight." If McGarvey's recent achievements are anything to go by, it should be the best-looking drink you'll see all year.