Imagine curating a display of photographs collected from the homes of millions of ordinary Britons. In order for your show to be remotely representative, it would have to include many shots of special occasions such as birthdays and anniversaries, and lots of people smiling, on holiday, with family, partners and pets.
Such an exhibition would not be representative of day-to-day life in our country. As Kevin Jackson notes in the catalogue accompanying Tate Britain's absorbing show "How We Are: photographing Britain": "A photographic exhibition is a quotation from quotations." However, it would reveal something about our aspirations and how we see ourselves. We don't smile and have fun every day, but what most people want out of life centres on family, friends and good times, and our photo albums reassure us that we have at least in part succeeded.
The Tate's exhibition, however, reflects a very different side of the nation. It represents the way in which professional photographers, often with artistic aspirations, have captured our country since the 1840s. Like a family album, however, it tells us less about how the subjects really are and have been, and more about what people behind the lens are looking to see. The camera never lies; it always tells a truth about the photographer.
The truth that comes over most strongly is that photographers who choose British life as their subject are often a miserable, misanthropic bunch. Zed Nelson's Love Me, for example, captures a young girl in a beauty contest looking like a forlorn puppy. The strange logic seems to be that, because a cheesy grin is de rigueur in posed photographs, somehow subjects are truly themselves only when they do not smile at all. By itself the picture is impressive, but the collection as a whole fails to show the richness of British life, because it does not counterbalance the overbearing gloom with sufficient light.
According to the curators of the exhibition, Val Williams and Susan Bright, British photography is "distinguished by its strong social conscience, a love of the ordinary, an intense curiosity and need to record. Above all, it is a medium of melancholic grandeur, tinged with nostalgia, which seeks to memorialise the past."
There is some truth in this description, but however much artists and intellectuals profess their love of the ordinary, they very rarely show it. Fergus Horn's picture of a suburban Surrey street is one example of a really everyday image, but it is not at all in keeping with the rest of the show, in which the truly normal is relegated to a few cameo appearances. The exhibition illustrates a common misconception that normality is by definition drab, miserable and depressing - and, far from showing a "love of the ordinary", it actually demonstrates a kind of hatred for it. This is a tendency that has grown over time: while many of the older photographs express some kind of optimism, the more recent ones generally accentuate the negative.
There are several examples of photographers finding beauty where usually we see none, such as John Davies's wonderful shot of a football field in the shadow of Salford Power Station. But even here, the implication seems to be that it is only the efforts of the artist that have elevated the aesthetic of everyday life from its sorry, lowly state. Britain's breathtaking natural beauty, for example, is hardly shown at all. It is ironic that the same photographers who claim to be able to find beauty in underappreciated urban settings are incapable of seeing it where everyone else does - in the countryside. Perhaps that would be too easy.
The curators insist that this is not a social history, but there is often a sense in which the subjects are framed not as individuals, but as social phenomena. Sometimes the commentary is so explicit that it feels like a harangue. Martin Parr, for instance, captures Morris dancers performing in front of a McDonald's; Chris Harrison photographs a Tesco superstore behind what looks like a civic war memorial. These images carry the subtle implication that ordinary people cannot see how modern life is debasing them. McDonald's and Tesco's - places where people love to go - are intrusions. Anna Fox's snapshot of a woman with Eighties hair and a mobile phone the size of a desktop computer is entertaining, but has the cultural value of a TV nos talgia clip show.
Photography is, however, a more democratic medium than most. There are two fascinating pictures of Queen Victoria and Prince Albert by John Jabez Edwin Mayall, which show that, long before Charles and sons were snapped smiling in their jumpers, British royalty made attempts to look informal. There seems to be a strange rule that formality in pictures should be inversely proportional to wealth: the poorer subjects tend to look smart and at their best, while professional photographers targeting more affluent demographic groups today offer shoots that make them look like models in a Gap advert.
The images that would truly manifest Britain's priorities and values are simply too hackneyed to find their way into an exhibition of art. There are no football crowds here, nor silver jubilee street parties, booze cruises, weddings and mud-clad festival-goers at Glastonbury, nor school photos. There is only one brilliant shopping photo, by Paul Reas: in a rare example of a subject looking genuinely unselfconscious, a rough-looking, unshaven young dad, fag in mouth, shows his unseen partner a war-themed roll of B&Q wallpaper for his bemused-looking son. It's a great shot, but again it focuses on those at the bottom of the social ladder, rather than the majority clustered around the middle.
Perhaps what the exhibition shows most of all is how fascinated certain sections of society have become with what it means to be British. Yet the answers offered here do not really tell us "how we are" - they are constructs, which frame the photographers' hopes and fears about our current condition. Perhaps if the Tate had contented itself with giving us an unprecedented overview of British photography, that would have been enough, but the insistence that these images should "say something" has trapped them in a journalistic role in which they seem ill at ease.
This is still an engrossing collection of images. And, of course, many of them do uncover things about the nature of Britishness, once you accept that they are filtered through the vision of a small group of artists. Visitors to this exhibition will appreciate what is being shown, rather than what is being said.
"How We Are: photographing Britain" is at Tate Britain, London SW1, from 22 May. For more information go to: http://www.tate.org.uk