Perhaps the most consistently visually innovative photographers Britain has ever produced, Nick Knight has been top of his game for over three decades, coming of age at the same time as London-based style magazines i-D and The Face made their indelible mark upon the world in the mid-1980s and still very much in demand with the likes of Yves Saint Laurent and Alexander McQueen. Not for nothing did Creative Review name him both 'Most Inspirational Photographer' and 'Most Admired Person in the Creative Industries' in its Ultimate League Table in 2001.

Despite his extraordinary back catalogue he's rejected many offers of a major retrospective show, something he seems to regard as an anathema to his commitment to constant reinvention, and his website displays just a limited selection of his work. But Knight is absolutely committed to his belief that online is where it's at, and nine years ago he put his money where his mouth was and opened Showstudio.com, sinking thousands of pounds into the project.

It features interviews with the photographer and his many collaborators - from erstwhile partner Peter Saville, the graphic designer with whom he worked with during his groundbreaking, early career fashion shoots for Yohji Yamamoto, to Bjork, Kate Moss, John Galliano and Heston Blumenthal - alongside experimental interactive artworks, behind-the-scenes reportage, and highly inventive films and live performances. Dedicated to pushing the boundaries of how fashion is communicated online, it's proved an award-winning formula, embodying the values he describes as 'process, performance and participation'.

Watching Naomi

For those familiar with Knight's work, the interest in process will come as no surprise. As far back as his photography degree, at Bournemouth and Poole College of Art in the early 1980s, he was playing with painting onto negatives, and after graduation he experimented with cross-processing and used a Scitex machine to elongate and warp his images. When Quantel Paintbox came along he was a natural early adopter. Working on his photographs, he started to question the concept of the 'decisive moment', and when art director Marc Ascoli picked him to work on designer Yamamoto's fashion catalogues in 1986, he had a moment of epiphany.

'Naomi Campbell came in to do a shoot, dancing to Prince on a piece of red Perspex with flashes and a red-headed tungsten light,' he recalls. 'It was so amazing, probably the most exciting visual art I could imagine at the time. But then I thought, "Nobody is going to see this - they'll just see the one, two or three split-second shots". I thought that was insane. Everyone was talking about "the moment" but they were missing all that. And they were also missing the weeks I sat reading books and talking to Mark about religion and philosophy and art and personal relationships.

'Then I expanded back to how I physically took the photograph - what was my physical relationship with the model? Was I looking up or down, was she empowered by my stance in front of her or feel dominated by me? The whole performance of creating an image became interesting to me. I don't just waltz in there like in Blowup. I work for hours sometimes trying to find a picture, and then I spend weeks in post-production.'

Knight started filming his shoots (and more), recording the whole process of creating fashion images. Soon this led to a second big idea - shooting fashion film. Designers create clothing that's fluid and accentuates movement, he reasoned, so surely it made sense to show them in moving images. Following in the footsteps of Guy Bourdin and Erwin Blumenfeld, who made some of the more interesting crossovers into film, Knight was determined to rethink the medium. He remains firmly convinced it's the future of fashion imagery.

'It's the medium that fashion photography was 30 years ago,' he declares, and Knight's videos are indeed hard to resist. For example, a recent shoot, Make Up Your Mind, features a faceless model in Maison Martin Margiela's spring 2009 'Wig Coat', gently moving to a quiet, tuneful melody. The effect is surreal and also slightly disturbing, and it's strangely compulsive.

But it wasn't until the web came along that Knight really found a forum for the work, and his behind-the-scenes shoots. 'We started thinking of Showstudio as soon as the internet came along,' he says. 'It was obvious it was a completely new medium that offered completely new opportunities.' Conceived by Knight and Saville 10 years ago as a website for art and fashion, it went live in November 2000. 'It allowed me to be more free with the material, and show the steps that went into creating it,'she says 'And the end result wasn't pinned on the wall or presented in a magazine in this arrogant, finite way. It was part of an ongoing conversation.

'I don't like the vision of the photographer who shuts people out and doesn't want to hear any one else's opinions. The pleasure of working is to get inside other people's eyes and see the world their way.'

Collaborations

And that's where participation, the third strand of Showstudio, comes in. Fashion photography is always about teamwork, but Knight seems particularly enthusiastic about creative collaborations, and he's always sought out the brightest and most avant-garde brains in the business, from stylist Simon Foxton to performance artist and self-styled muse Leigh Bowery. But he's also used Showstudio to open fashion up to the wider world, asking visitors to contribute ideas for stories, for example, and putting footage for them online to edit.

In fact, this democratic approach underlines his approach to showing work too. Long courted by the art market, Knight has largely resisted attempts to put his work in galleries, and he only agreed being included in The Photographers' Gallery next exhibition, When You're A Boy: Men's Fashion Styled by Simon Foxton, because the stylist is an old friend. And his forthcoming exhibition at Somerset House centres round a live incarnation of Showstudio rather than static displays of long-completed images. Fashion photography excites him because it reaches so many people, he says, and putting work online is just the modern-day equivalent.

'If people randomly see my images on the back of a magazine there's no preconception about how they should judge them, they're just the vernacular of what they see,' he says. 'That's how photography works best. But if you want to speak to people, and what I do is communication, then there's no point in going and speaking to very few people when you could speak to many more. A magazine might have 10,000 readers, but I can reach 10 million people through the internet. It's the medium best suited to where we are now.

'I have three kids. My youngest is just 12, and the oldest is 16,' he adds. 'They don't pick up magazines, and we have lots of them in the house. They look at the internet, talk to their friends across chat rooms and social networking sites and go on YouTube. That's the reality. It's different media, different ways, and I want to work on the medium where the most interesting things are happening. Taking a load of photographs and putting them in a magazine that nobody looks at is very unappealing. Creating a set of photographs to hang in a gallery for some of my friends to go and see holds no interest whatsoever. We're looking at a completely different set of values.'

Last generation

What he puts online is a moot point though, because while Knight still shoots still images (for very prestigious clients), he prefers to use moving images on the web. It's the content most appropriate to the medium, he says, and he's sure other image makers must be thinking the same thing too.

'I'm one of the last fashion photographers,' he says. 'If I was 15 right now, I wouldn't want to start working for magazines, because they're clearly not the most interesting thing around. Other people must be thinking the same thing. They're looking through the magazines and thinking, "There's no excitement in these things any more because they're just dolling out the advertisers' lines and products". All the excitement is over there on the internet.'

But working online doesn't just mean making moving images - Knight has been involved with 3D imaging since 2000, when he used a 3D scanner to create a project with stylist Jane How. He's since created 3D scans of models Liberty Ross and Naomi Campbell, and is turning these models into solid, real-life sculptures. 'I'm using the mechanical optic in just the same way as the photographic optic, thinking about form and space,' he says. 'In a way I'm not doing anything that different, and I'm interested in how close that is. That's the next step.'

And, in fact, that constant innovation is what drives his restlessly creative mind. Photography is changing, and fashion photography in particular is always evolving, he says. The trick is to embrace it. 'When you take a photograph you're predicting the image you'll capture when the shutter falls,' he says. 'You're working in the future. That's where I like to be working, in everything I do. I like doing all these things that haven't been done before.'

See more Nick Knight, a retrospective of the photographer's work since 1990, is published by HarperCollins on 27 October (ISBN: 9780061714573), priced $75.