Thomas Sutcliffe: Painters turn their backs on art

If you were in a mischievous mood you could describe the Hayward's new show "The Painting of Modern Life" as a major retrospective of backs. I mean people's backs – the portrait's B-side, which we rarely see in an art gallery but which are all over the place here, sometimes centrally placed, as in David Hockney's painting of two friends sitting in the Parc des Sources in Paris or Peter Doig's picture Lapeyrouse Wall, and sometimes incidental, as in Malcolm Morley's picture of a group of passengers on a cruise liner or Johanna Kandl's painting of the Venetian waterfront.

In fact, there are an astonishing number of backs in here – a point picked up in a catalogue essay by Carolyn Christov-Bakargiev, though even she doesn't give a complete inventory of the backs on show. You can't really blame her; well over half of the artists here include paintings of people's backs, even on a conservative count. And as you wander round the Hayward it starts to have a slightly odd effect on you, this collective repudiation of the established etiquette that a subject should look out of the picture at us, rather than into it at something else.

The odd effect is the point, of course. "The Painting of Modern Life" is a collection of works that have all been painted from photographs, and this is a show that depends on the residual charge that a mechanically captured image leaves in a painting, however altered or worked over that original image is. At first I thought it was a matter of time alone. A photograph is essentially coterminous with what it shows us; that is, the time it takes to make a photograph is a close fit with what is depicted. If it isn't, the photograph usually lets us know, by blurring or loss of focus. In a painting, by contrast, the time taken to make the picture bears no direct relation at all to what it shows. An instant that might last half a second may take half a year to recreate... and that does something significant to a picture. Put the two together, so that entirely different assumptions about time clash with each other, and you get a galvanic charge.

But that doesn't seem quite enough to explain the strange atmosphere in most of these paintings – their shared fascination with the banal and the contingent. It isn't true of all the works here. Warhol chooses dramatic news pictures as the basis of his paintings. Hockney appears to use it only as a tool in the construction of self-consciously painterly compositions. But most of them cherish what Baudelaire, in the essay that gives this show its title, described as "the transient, the fleeting, the contingent". These are the sights you see out of the corner of your eye when you're concentrating on something else – ordinary streets and interiors in which nothing particularly special is happening.

Indeed, some of the artists are explicit about this. "The photos I use aren't always that interesting or distinguished," says Doig. "With photographs, you notice that you don't even see people sometimes. There's so much else going on that you don't really know what they look like," explains Elizabeth Peyton.

What would traditionally count as a failing in a painting – a cluttered composition, an inertness in the image – has been transformed into a virtue instead. Indeed, you can tell quite a lot about what photographs do for these artists by thinking of the photographs they don't use. They're not interested in anything that has a sheen of aestheticism to it, only in pictures that display that promiscuous carelessness which is a feature of photography. Take loads, we'll see which works best later.

And all those backs – so indifferent to the act of picturing which is taking place – give a clue as to what it is that photography really supplies for these artists. It's the ability to disappear and not be scrutinised any longer. Again, some of them are quite explicit about this: Gerhard Richter identifies the value of photography as being "not having to invent anything any more, forgetting everything you meant by painting – colour, composition, space".

It's a kind of abdication in a way, a means of laying down the burdens of executive responsibility that the Artist usually has to bear alone and enjoying instead the artisan liberties of a workman. Don't ask me what it means guv – someone else took the picture. If it's trite or drab, that's the world's fault, not mine. Paradoxically – because there are seriously good paintings by serious-minded artists here – it's the most Artless show the Hayward has put on for a long time.