Tony Wilson, their label boss, is dead now. So is their manager, Rob Gretton, and their producer, Martin Hannett. Their lead singer, Ian Curtis, tormented by epilepsy and torn between his wife and lover, hanged himself on May 18 1980, on the eve of their first US tour. But in Anton Corbijn's new film, Control, Curtis, Joy Division and their extended Manchester family live on.

It is the second major film about these four northern musicians, their home town and the characters in their orbit, following Michael Winterbottom's 2002 movie, 24 Hour Party People. "It's amazing enough to have one film made about us while most of the principal characters are still alive, but to have two films is quite bizarre," says Joy Division/New Order drummer Stephen Morris. He adds that a third "biopic" (a word everyone in the band loathes) was mooted at one point, and that a feature-length documentary, simply called Joy Division, will go on general release just after Control.

For bassist Peter Hook, the documentary, which will be premiered at the Toronto Film Festival in October, is the perfect companion piece to the movie. "I couldn't believe how well it goes with the film," he says. "It captures the Manchester of the 1970s so well. Control doesn't feel like the end of the story; the documentary closes things off perfectly. But Anton's film is more chilling. Towards the end, it felt like someone had ripped out my heart and was stamping on it. To be honest, when [the Joy Division song] Atmosphere came on, I thought I was going to throw up."

According to Bernard Sumner, Joy Division/New Order's guitarist (and unofficial musical director, making him one of the key figures in the development of electronic-based rock music of the last 30 years) it was only right that Curtis should provide the focus for Control.

It was also crucial that "the story should be allowed to tell itself, before any kind of self-expression from Anton", he says of the Dutch director, whose photographs of Joy Division when he was an NME photographer set the austere, modernist tone for the post-punk era. (Control is filmed in black and white.)

"Ian is the central character, not Anton," says Sumner. "I think people want the story. I really like the look of it. That's pretty much how it was, really. Maybe the band's characters have been suppressed a little. We were more youthfully idiotic than that. But we had a serious side. We stamped our personalities on the music of Joy Division and it sounded heavy. But we weren't really heavy people. I'd had quite a tough life up to that point. I'd had to cope with a lot of death and illness in my family from a young age, and that maybe gave me a bleak outlook on the world. But looking back, we were flippant and playful. It's just that, when we got in the rehearsal room, that's the music that came out of us. Overall, these aspects of the band are captured very accurately in Control.

"The guy who plays Ian [Sam Riley] has done an amazing job. Ian had a very explosive side that only comes out once in the film; his way of dealing with problems was to explode. But human beings are complicated creatures. It's impossible to capture every single facet of someone's personality in a film."

Corbijn, who makes his directorial debut with Control, was drawn from the Netherlands to England in 1979 by Joy Division's spectral music and Curtis's haunting voice. Within 12 days, he had taken the now-famous photograph of the band in a subway passage. He is astonished by how closely Riley resembles Curtis, and delighted that an unknown actor assumed the role with such precision.

"Sure, we looked at some better-known actors: Jude Law was one of the names mentioned early on, but not by me," he says. "Sam comes as close as it's possible to get, I think. It's really uncanny." Control is based, in part, on Touching from a Distance, the memoir by Curtis's wife Deborah. She visited the set a few times, Corbijn says, and saw Riley playing her husband: "By the end she was calling him Ian."

Corbijn says Control takes its title from two elements: the Joy Division song She's Lost Control, and from Curtis being "something of a control freak, although the one element in his life that he couldn't control was the epilepsy". But why is it more about Curtis than Joy Division? "Because I was interested in the story of Ian Curtis. Joy Division are covered in the story but I wasn't interested in making a rock movie. The appeal of the film is far beyond Joy Division. It's a three-sided love story and a human drama."

The drama begins with the 17-year-old Curtis in his parents' Macclesfield flat, dreaming of David Bowie, Iggy Pop and Lou Reed, applying eyeliner and secretly smoking fags. Within five years, inspired by a Sex Pistols performance at Manchester's Lesser Free Trade Hall, he has become a star in his own right. By the climax, driven to the brink by illness and torment over his divided feelings for his wife and Belgian lover Annik Honore, he takes the decision that gives the story its tragic denouement and affords him legendary status.

Corbijn is certain about Curtis's motives for killing himself. "Being torn between two women would not normally be a recipe for suicide," he says. "It was the epilepsy that unravelled him. The drugs he had to take for that had such incredible side effects. Combined with alcohol, that gave him heavy mood-swings. But if two women love you, that doesn't mean you're going to kill yourself. It comes from somewhere else.

"I think he was caught up in this obsession with becoming someone. He was drawn to legendary rock stars such as Jim Morrison. Poetry and music became his focus. And something came over him when he was on stage. That made him enigmatic for people watching. He was mesmerising."

In Control, Curtis is portrayed on his last night alive, listening to Iggy Pop's The Idiot and watching Stroszek, a 1977 movie by Werner Herzog about a man from Berlin who is released from prison and goes to America in the hope of finding a new life, before committing suicide. The parallels between the character and Curtis, a day away from Joy Division's first US tour, are obvious. "I wouldn't want to speculate," says Corbijn, "but maybe other things - the music he was playing, the film he was watching, the alcohol - contributed to his decision. Maybe there was something in him that wanted a finale."

Sumner, Hook and Morris were all mortified, sitting through Control, that they couldn't see just how much pain Curtis, who had previously attempted suicide in April 1980, was in.

"The police described it as a textbook case: suicide brought on by depression, well-documented by his cries for help," says Hook. "Unfortunately, we were all too young to understand."

"This sounds awful but it was only after Ian died that we sat down and listened to the lyrics," says Morris. "You'd find yourself thinking, 'Oh my God, I missed this one.' Because I'd look at Ian's lyrics and think how clever he was putting himself in the position of someone else. I never believed he was writing about himself. Looking back, how could I have been so bleedin' stupid? Of course he was writing about himself. But I didn't go in and grab him and ask, 'What's up?' I have to live with that. Watching the film, there were moments when I wished I could have stepped into the film. Unfortunately, you can't."

"We never really listened to Ian's lyrics, to be honest," agrees Sumner. "At least, we never sat there and analysed them. It's a bit like reading your friend's letters, I suppose. But when he died, I did go through his lyrics and find myself thinking, 'Oh, God.' You look at it through a different filter because of what happened."

So why does Sumner, who became Curtis's successor as the singer in New Order, believe it did happen?

"Ian's problems were insurmountable. Not only did he have this hideous relationship problem, he also had this illness that he contracted at 22. And it wasn't a mild form. It was really, really bad and it occurred frequently. Then he had this explosive personality. The epilepsy must have cast a shadow over his future, particularly his future with the band, and his relationships cast another giant shadow. Plus, he felt extremely guilty about his daughter Natalie [13 months old at the time of his death] because his relationship with Debbie was deteriorating. I remember him telling me he couldn't pick Natalie up in case he had a fit and dropped her. That really disturbed him. At that age, no matter how mature you feel, that's a bloody lot to have on your plate.

"Then he was in a gigging band. Before he died, we'd spent four years becoming Joy Division. It revolutionised all our lives because we were small-town boys: Steve and Ian came from Macclesfield; Hooky and I were from Salford. We'd spent two years playing dives and dumps, and we were finally on the cusp of becoming really big with a tour of America. Nowadays, people fly to New York every day to go shopping. In those days it was a big thing. We were all so excited about it. But, for Ian, there was the thought of going over there and having fits in front of people during a gig. Sometimes a drumbeat would set him off. He'd go off in a trance for a bit, then he'd lose it and have a fit. We'd have to stop the show and carry him off to the dressing-room where he'd cry his eyes out because this appalling thing had just happened to him. The heavy barbiturates he was on seemed to compound the situation; they made him very, very sad. I just don't think there was a solution to Ian's problems."

And yet, in the wake of Curtis's death emerged New Order, who affected British electronic dance music as powerfully as Joy Division did UK guitar music.

The band acknowledge that the shift from Joy Division to New Order saw a transition from dark to light; the three surviving members, augmented by Morris's girlfriend Gillian Gilbert, managed, either by accident or sheer force of will, to create coolly calculated yet wrenchingly emotional pop from the wreckage.

The story of Joy Division and New Order has gripped music fans for nearly 30 years, but this summer it seems, at last, to have ended. Just when you'd imagine a film about their early lives might bring them closer together, New Order have split up. As Hook, currently in dispute with Morris and Sumner over the band's future, puts it: "We're fighting so much at the moment." But Control reminds him of the contribution these warring partners have made to the culture.

"It makes me realise that that part of my life was very special for a lot of people. It helps to remember that when I'm going through a lot of shit in my life like I am now. When I feel like I've achieved nothing. The break-up of a relationship is always difficult, especially a 30-year one. When I look at the film, it makes me realise that Joy Division changed the world. That's fantastic."

All three members agree, more or less, on Joy Division/New Order's position in the scheme of things. "When I listen to Nirvana, I hear [New Order's] Ceremony bass line on quite a few of those songs. So I'd have to say, yes, we are the missing link between the Beatles and Nirvana," says Hook. "I'd agree with that," says Sumner, who declines to comment on the split. "But really I think we were a strange anomaly that came out of the north and south of Manchester that just happens to have had some profound resonance with people. When we wrote our music we had no idea it would have that effect. Seeing other people play it in the film made me realise how great it was, and is."

"It's not for me to say whether we're the most important band since the Beatles," says Morris. "I just happened to be in a group whose music I loved. When you're doing it, there's no intent in terms of being historically important. I can only see it as a time of my life that has now been documented in two films. But it's horrible to think that someone has to die before they make a film about you."

· Enhanced versions of Joy Division's albums are released by Warners on September 10. Control is released on October 5. The documentary Joy Division will be out in 2008.