Is it art, or is it cashing in?

A 15-year-old magazine photograph of a naked Carla Bruni fetched 23 times its estimate at auction, raising the stakes in the photographic world. Sophie Heawood reports

We all know about Carla Bruni in the nude and yet it was still surprising, shocking even, that the photograph – taken 15 years ago by Swiss photographer Michel Comte – fetched nearly 50 grand at auction last week. Did the publicity around the state visit to Britain drive up interest? Not so, says Christie's; the timing of the sale was a complete coincidence. A likely story, you might think – until it becomes clear how many other photographic portraits they have sold this week alone (nearly £9m-worth) and how huge the market for photography as art has become.

Philippe Garner, Christies's international head of photographs, based in New York, explains that the Carla Bruni shot was just one item in a private collection also containing shots of Kate Moss, Naomi Campbell and Gisele Bündchen, taken by photographers including Richard Avedon and Irving Penn. The Bruni shot by the lesser-known Comte was thus "a relatively minor piece", brought to prominence only by the current fame of the subject, not the artist. The sum it raised – £45,500 – was easily eclipsed by that of other items, though it did at least achieve the biggest multiple of its original estimate, which was a rather meek £2,000.

So does this mean that everybody who has photographed Bruni, during her modelling and music-making careers, will now be jumping to flog their shots before her 15 minutes end? British music photographer Kevin Cummins thinks not. He photographed Bruni last year for a Times article about her music, and says he doesn't anticipate a rush on his stock – because, alas, "she kept all her clothes on".

The men's magazine GQ managed to run naked pictures of Bruni in its April issue, though strategic placing of her arms and legs mean you can't actually see much beyond acres of expensively oiled flesh.

"We had to ask permission from her to re-use the shots, which originally ran in French Vogue two years ago," explains GQ's picture editor James Mullinger, "and her people said we couldn't use any of the ones with her breasts exposed. Then she had some other issue with them but we'd gone to print by the time we found out, so it was too late." Does Mr Mullinger believe that these saucy magazine shoots should really be being treated as art, or is it just a nice bit of smut? "Without wanting to sound overly arrogant, yes I really do see this as art," he says.

But why are record prices being paid for what Garner calls "great editorial photography"? Many of the Christie's pieces were commissioned for magazine shoots originally, before being reprinted. Buying a photograph is not like buying a one-off work of art. Mr Garner says the Bruni shot was "an early print with a little airbrush work – and though Comte still holds the negative, I'd be surprised if he would consider making another edition, as that might give him the reputation of a one-photograph artist".

He says the market started to swell at the turn of the millennium, "when the 20th century became a quantifiable, defined period of history. These photographs provide beautiful memories of the recent past". The rise of digital photography means "there is now an unprecedented demand to buy prints from the masters of that heroic era of roll film".

Back at GQ, Mr Mullinger is more optimistic about contemporary photography, but that's because of the subject matter.

"With women like Kate Moss and Carla Bruni, we haven't seen such sirens since the days of Marilyn Monroe and Ava Gardner," he says. Brett Rogers, director of the Photographers' Gallery, adds: "The Bruni image is interesting to me only in so much as it falls into the realm of politically connected iconic nudes which is perhaps best exemplified by Lewis Morley's infamous 1963 photo of Christine Keeler seated on a chair.

"At present the demand from a new generation of collectors interested in the crossover between celebrity and fine-art photographs is unprecedented."

So who is the mystery buyer, said to be a Chinese art collector, who has bought Bruni to adorn his mantelpiece? Christie's can't confirm anything, but Mr Mullinger says the picture would make the ultimate addition to any bachelor pad. "It's a step up from the Loaded generation having a poster of Michael Caine in Alfie. But this guy is clearly not the most astute collector, as it can only depreciate in value."

Mr Cummins agrees: "You see record prices being paid for paintings nowadays but you know they're only going to end up in bank vaults because they're too valuable to insure and exhibit. Whereas the Bruni picture is definitely going on somebody's wall. It's gone to some 'look-what-I've-got' bloke."