All the items in the V&A exhibition come from the collection of New York's Museum of Modern Art. In that Manhattan temple of the avant-garde, all works of art - and especially photographs - lose their context as they join the great onward march of cultural history. Now, we can rhapsodise about the glorious flash in Weegee's picture (above). We can praise the perfectly balanced composition of an image taken on the run amid the usual scene-of-crime mayhem. The shutter stays open, but the case is closed.
Time has an odd, denaturing effect on photographs. Slowly but surely, they check out of Life and into Art. And this diverse exhibition reveals as much about that process as it does about America itself.
Weegee - an immigrant hustler whose real name was Arthur Fellig - shared with many news photographers a yearning for prestige and recognition. In the pre-war heyday of the gangland wars, he chased bells and sirens to deliver gory front-page splashes to New York's sensation-hungry papers. Cops believed that some uncanny sixth sense led him to reach the hot spots before they did. In fact, he listened in to their communications. This brilliant scavenger sought, and found, smarter assignments: for instance, in his pretentious 1948 book of Weegee's New York. But he never equalled the impact made by his rough and cunning life of crime. His most functional shots pack the hardest artistic punch - a pattern you can see repeated throughout the V&A selection.
The other striking aspect of this picture is the way that it resembles a still from some gangster film. It's a group reaction shot, with the main action off-camera and the drama of the killing intensified by Weegee's characteristic super-strength flash. Hollywood shadows this epoch of US photography from start to finish. Remember: lightweight, portable cameras only arrived on the mass market with the release of the Kodak No 1 in 1888. In other words, photography as a cheap and mobile art is not much older than the movies.
In the US, it shared from the outset their taste for novelty and their relish for violence and scandal. From the view of Market Street in San Francisco ablaze after the 1906 earthquake to Gary Winogrand's shot of tourists in Dallas gazing at snaps of the Kennedy assassination site, sudden blows from God or man run through the V&A show like a bloodstained thread.
Another photographer who matches Weegee's relish for rackety low-life is Gordon Parks. In 1948, he captured some scrawny teenagers as they scrapped on the streets of Harlem. In those days, Parks was a Life magazine staff photographer. Later, he aged into the king of blaxploitation movies, director of such meretricious landmarks as Shaft. How strange - but how American.
Still images in magazines also vied with moving pictures in building up the American cult of celebrity. And that has always proved a two-edged sword for its targets. Worship and contempt fused as each successive star was born. Nickolas Muray's famous 1927 portrait of Babe Ruth, baseball's Pele or Bradman: the sporting idol squares up the lens as if he fears and despises it. And so he should - Ruth was a thug and a tippler who lived in an age when a pliant media generally glossed over the foibles of popular heroes. But Muray can't quite manage that cosmetic sheen. Something gross and menacing - a Gazza-like quality, perhaps - survives the formality of the portrait sitting. In this case, at least, the camera really hasn't lied.
`American Photography 1890-1995' is at the Victoria & Albert Museum until 26 January, 1997. Tel: 0171-938 8500.