ART / Exhibitions: Life, the universe and everything: The Hulton Deutsch Collection contains 15 million photographs. Out of it the Barbican has made the first unmissable show of 1994

IT WILL be a long time before we see another photography exhibition as good as 'All Human Life'. Occupying both floors of the Barbican Gallery, it is so crammed with interest that visitors should allow a couple of hours to absorb its message. And it's not only large. The images, some 400 of them in all, are both vivid and suggestive. They tell us something that fine art doesn't: other people's experience of the world is uniquely captured by photography.

Or by one kind of photography. This exhibition is a fine tribute to British photojournalism, and its prints have the virtues of the best journalistic writing: they are informative, anecdotal and humane, and their initial interest is rapidly replaced by historical importance.

Rapidity is of the essence. Photojournalism gathers things swiftly, therefore without pomp or posing. Informality is a virtue and the grand manner to be avoided. Photojournalism is intimate and sympathetic. It leaves moral judgements to other people. There's lots of art in it, as we can see here; but photojournalists don't like to go on about art, because their overwhelming concern is with what goes on around them.

'All Human Life' is taken from a single but vast source, the Hulton Deutsch Collection. This was originally the library of Picture Post, but it has absorbed some 50 other archives over the years and now holds no fewer than 15 million photographs. Picture Post also kept historic photographs in its library, so there are prints in the show that long predate the era of that famous magazine. The selection has been done by Bruce Bernard, former picture editor of the Sunday Times Magazine and the Independent Magazine. Of course, as he ruefully admits, he hasn't examined every photograph in the collection. But he has brought us a wonderful fraction of the whole, presented with the skill and panache of an old-school newspaperman.

I think of Picture Post as one of the great products of Attlee's Britain. Conceived in 1937, it excelled as a magazine in the years after the war. The heart of the Barbican exhibition is in this period, and I find that the 19th-century photography doesn't match the later work. We all know about the historical place of Lewis Carroll and Julia Margaret Cameron but I weary of having to appreciate such pioneers yet again. And, beautiful though some of them are, in these old albumen prints there is not just a Victorian heaviness but a pervasive brown melancholy. There's even something furtive about their atmosphere, as though photography had yet to declare itself.

Then, quite suddenly, Bernard's installation places us in a contrasting room, which he calls 'Brave New World'. These pictures are mainly from the Thirties, but they go up to the Fifties. Here are pictures of a new technology that was inseparable from style: Sir Nigel Gresley's splendid, slightly art-deco locomotives rest in a marshalling yard like modern beasts; a streamlined van shows itself off, futuristically designed, reminding us that this was the heyday of science fiction; the Graf Zeppelin looms; a starlet arrives at a party carrying an early television; a room from Olympia's Ideal Home Exhibition makes one wonder about ideals. Now we see shared but quite glamorous values that were disseminated through the media. And interspersed with these quick studies are fascinating interior shots of, for instance, laboratories and power stations.

Quite a number of these prints are anonymous. Although the exhibition contains work by well-known photographers such as Kurt Hutton and Bert Hardy, it also insists on unknown artists. These lensmen, whoever they were, simply filed their work with an agency, didn't necessarily see it published, or if they did, were often not given a credit. I write 'lensmen' deliberately, for the great age of photojournalism seems to have been masculine. Perhaps there were women in the business who were even less likely to be credited. Note, though, that Bernard makes women's work a strong theme of his exhibition. Often this is delicately conveyed. What a lovely picture is George Douglas's Lady Sweep of 1951. He had found the last woman chimneysweep and snapped her with a glass of beer after her labours. The image is about the persistence of 19th-century life in the modern world. And quite apart from the way that it's sexually mysterious, there's an intriguing ambiguity about the sitter's age.

Her occupation, too, is unclear. Explanation is essential. Photojournalism has no fixed rules but is most effective when accompanied by words in a magazine format. Many pictures in this show would be baffling if presented without captions. A photo of a man in an empty, dilapidated ballroom is called The Loneliest Man in the World. You do need to know that he was the caretaker of a grand hotel in Holborn that was closed throughout the war. I like words and photographs together. They help to satisfy, but also to stimulate, the instinct of curiosity. A task of both serious and popular journalism is to sense the public desire to be inquisitive about other people. An undervalued function of Picture Post in the Forties is the way it presented everyone in our society - servants, typists, engineers, celebrities or toffs - as though they had an equal right to be interesting.

The contrast is with the class stereotypes of Punch. These were amusing in a predictable way and never dug deep. Bernard very properly has a section of his show that contrasts rich and poor. How deeply these images affect the viewer will depend on who the viewer is. Photojournalism tells you all sorts of things but it doesn't aim to make converts. Photographers are seldom crusaders. Nor - surely this a reason why so many of them remain anonymous - do they wish to impress us with their individual talents or their unique personalities. They are the most democratic of artistic people.

It's hard to describe the purely aesthetic impact of 'All Human Life'. I'm not a critic who claims that photography has the attributes of more traditionally valued art - composition, exquisitely graded tones, etc. I care about such things in painting, hardly at all in photography. I like what we find at the Barbican, photography's dramatic and intense enlargement of our visual knowledge of the world. The camera fails most often when it makes a conscious attempt to contribute to fine art. Photojournalism fails if it doesn't grasp a visual point, but it never even runs the risk of being phoney.

No space here to describe all the things that are engaging, troubling or exhilarating in the photos at the Barbican, but space enough to lament that photojournalism's golden age has passed. When? Probably with the ubiquity of television, in the late Fifties. TV deals often enough with the same sort of subjects as classic photojournalism, but never to the same effect. Who would wish to see an exhibition of stills from TV documentaries? 'All Human Life' celebrates a previous age of the camera, and it makes me think of so much that has been lost - including the memory of that chap who might have been a rather good Picture Post photographer, Clement Attlee.

'All Human Life': Barbican, London EC2 (071-638 8891), to 24 April.

Overleaf: Hilton on Modigliani

(Photographs omitted)