Lunchtime in Soho, and the Photographers' Gallery is packed. Earnest students with bulky camera bags stand in front of John Davies's paradoxically beautiful English landscapes - monolithic tower blocks, industrial wastelands, urban nightmares - and appraise each image solemnly.
The bookshop and the café are full of wannabe collectors and amateur snappers. Yet upstairs, in a quiet meeting room, the gallery's director, Brett Rogers, is telling me that, no, she can't take a picture to save her life, and that she doesn't even try. "God, I don't take photographs," she says, horrified. "My children, rightly, think I'm rubbish."
Tomorrow night, David Furnish, partner to Sir Elton John and significant collector of photography, will present the annual £30,000 Deutsche Borse Prize to one of four nominees currently showing at the Photographers' Gallery - Davies, Jacob Holdt, Esko Mannikko and Fazal Sheikh. It's the biggest week of the year for Rogers and her staff, culminating in a flashy party attended by the likes of Tate Modern director Vicente Todoli, architect Lord Rogers and designer Nicole Farhi.
"This is our flagship show," confirms Rogers "and this year, unlike last, which was much more arty and detached, each nominee is connecting in some way to a social or political issue. Perhaps it's in the zeitgeist, this need to get to the crux of who we are as human beings."
Indeed, the 2008 show makes for (mostly) sombre viewing. Sheikh's entry features unsmiling portraits of abused women and girls in India; Holdt shoots a drug-using American underclass; and Davies's images, gorgeously printed, detail an English countryside uglified and scarred by human industry. Only Mannikko, the joker of the pack, raises a smile with his brightly coloured, quirky take on life, both animal and human, in northern Finland.
Yet for all the glamour and City money surrounding the prize, for all the rock star collectors - Sir Paul McCartney is another enthusiast - London is still the poor relation when it comes to photography.
It is an art form that has always been undervalued here. New York, Paris and Amsterdam all beat London hands down for world-class facilities and state-of-the-art galleries (the first two have established national museums of photography). The world's largest festival of photography takes place each year in Arles, France.
The recent, and 11th-hour, cancellation of this year's London fair, Photo-London, is symptomatic of the lack of importance attached to the medium here. (The festival's organisers were drafted in from Paris and, without local knowledge, scheduled the event for a spring weekend in the middle of the empty City, thereby guaranteeing its failure. Last year's event at Old Billings-gate drew just 7,000 people.) As Martin Parr, perhaps Britain's only householdname art photographer, says: "London is by far the lowest in terms of pecking order when it comes to photography."
But Rogers, the 54-year-old, down-to-earth Australian who cannot work a camera, aims to change all that. "In contemporary art, we've really led the way - with galleries like the Serpentine, the Whitechapel, and of course Tate Modern. But somehow photography has lagged behind. I wonder whether, historically, there's been something in the British psyche that has a block about it? The point is, we now have enough major collectors and enough will to make a radical move, and to reinvent ourselves."
Next year, then, the Photographers' Gallery in Great Newport Street will shut and work will begin on a new, cutting-edge £15.5 million building in Ramillies Street, just off Oxford Street.
"We just can't continue in this current space," says Rogers. "We're too cramped, we're too constrained. We can't ever borrow from [international archives] Getty or MoMa because we haven't got the right environmental conditions. There are still artists who won't show here because it's just not slick enough. We have to provide them, and of course the visitors, with facilities that one expects of a 21st century gallery."
The new building, by Irish architects O'Donnell + Tuomey, is designed to put London on the international map, with three distinct gallery spaces allowing the display of large-scale work and more challenging subject matter. The print sales department will be more accessible, and the bookshop will expand into a reading and resource centre for hobbyists and professionals alike.
Rogers still needs to raise £8 million of the total cost (the rest will come from Lottery funds) and acknowledges that the credit crunch and a depressed City make that job much harder. "It's a very tough climate out there and we honestly think most of the money will come from private individuals, rather than corporates, who see photography as the most accessible art form out there."
She reveals that she has been trying to talk to McCartney about naming one of the galleries after his first wife, Linda, the rock photographer - but "it's a discussion we'll have later: he's got other things on his mind right now".
Yet a miserable economy is potentially good news for photography, too. In general, photographic prints are cheaper than contemporary art - though the biggest names in international photography can sell for small fortunes: Richard Prince's pictures go for £500,000 while Andreas Gursky has attracted a £1.7 million price tag.
If the City bonus this year does not run to a painting worth £10,000, it may still buy you a top-quality photo at £3,000. You can buy at the Photographers' Gallery for £300-£500.
"It's part of our remit to start people collecting," says Rogers. "People feel intimidated about going into chi-chi galleries in Mayfair and asking perhaps naïve questions about art, but with photography that's less of a problem. We want to educate people and we don't mind those sort of questions at all."
In an indirect kind of way, Rogers came to London because of photography.
"I grew up in the Sixties and my whole image of Britain was formed through photos in magazines. I used to cut out those images of fabulous swinging London from Vogue, Nova, Harpers & Queen and so on, and stick them on my wall. London was the place to be - and I wasn't there. That's how I fell in love with Britain and that's why I came. I still think of photography principally as being a vehicle through which we understand other cultures."
Rogers has been at the Photographers' Gallery for little more than two years, but was a force in British photography before that as deputy director of the Visual Arts Department at the British Council.
"Once you start working here and realise what a wonderful cultural wealth this city has, you can never ever go home," she says. And during her time in London, of course, she has seen huge technological change - the arrival of digital photography, the ability to print images instantly, the use of the internet as a tool to disseminate work.
In response to this, on the ground floor of the new building in Ramillies Street, she is going to install what she calls the Democracy Wall. "We want people to come into the café and upload pictures directly from computer terminals or laptops onto the wall of the gallery. She pauses and grimaces. "We'll have to moderate that very carefully of course."
In no other art form, indeed, are there so many amateur practitioners. Yet for Rogers the difference between a good amateur and a seasoned professional, or artist, is still easily defined. "It's not just about technique but sustained commitment. The art of pursuing photography in a concentrated way is very different to producing one or two good photos. All four nominees for this year's Deutsche Borse Prize show us how, over time, you build up layers of meaning and history - something you just can't get with the quick shot. It's about having a body of work that deserves attention." At the same time, she insists, the Photographers' Gallery is not a snobbish institution.
"The democratisation of photography is a great thing. People are much more sophisticated nowadays at reading photography and it's up to us to take that visual literacy and enhance it. Oh yes, we are all photographers now." Everyone, that is, except for her.