Seduced by Art, National Gallery, London

Photography has arrived at the National Gallery, but it is being greeted with more of a sigh than a cheer. Listing the American "sister institutions" that include photographs in their collections, Director Nicholas Penny writes that "we have realised that we should give more attention to photography". The tone of reluctance is unmistakeable. For the time being this suspicious alien is being detained in the basement of the Sainsbury wing while his credentials are examined.

Seduced by Art is the first fully-fledged exhibition of photography to be staged here, but it is an ambiguous beginning. In aesthetic terms, photography sprang from the older arts, just as the automobile sprang from the hansom cab. And the early photographers shown here such as Julia Margaret Cameron owe everything – subject matter, poses, background, the mood of sentimental piety – to Old Master paintings.

Compared with painters, their means were meagre: all they could adjust were subject matter, framing, light and shade, focus. Colour was unavailable to them – so why did the poet Elizabeth Barrett say of daguerrotypes that they were "the very sanctification of portraits"? For one reason: immediacy. It is not that the eyes of a Cameron waif are more precisely reproduced than a painter could achieve: it is that they are alive, they are with us, in a quite different way.

But in Seduced by Art this crucial difference is downplayed in favour of curator Hope Kingsley's vision of how, in our time, the photographic prodigal came home. From the early days, we leap 140 years to very large colour photographs which aspire to the same grand, classical effects as the Old Master paintings upstairs. But these attempts are cul-de-sacs which, far from developing photography's potential, only point up its relative weaknesses.

Richard Billingham's attempt to out-Constable The Cornfield; Maisie Broadhead's embarrassing restaging of Vouet's Allegory of Wealth; Simon Norfolk's deliberately wooden, sepia-coloured, posed portrait of British soldiers in Helmand: these and others show photographers sacrificing the single peerless quality of photography – immediacy – in the quest for something chimerically classic.

A century ago, photography's verisimilitude set fine art free to invent Impressionism, Cubism and the rest; there is no point in photography now offering itself up in chains to gain entry to this establishment. But there is another way: the best works in this exhibition show the inspiring effect that tradition can have in the right photographers' hands.

In 132nd Ordinary Meeting of the Conference, former Newsweek war photographer Luc Delahaye demonstrates a genuinely creative way to absorb Old Master influence in his portrayal of an Opec press conference. The huge scale, the rich yet subdued palette, the symmetrical framing, all convey an impression of solemnity and historical weight – one that is fatally subverted by the chaos as reporters, photographers and cameramen struggle this way and that to get the best angle, quote, image.

One Flesh by Helen Chadwick radically reinvents Madonna and Child paintings, piecing the elements together from photocopies of the actual objects; the "Madonna" is Chadwick herself, in the act of cutting her baby daughter's umbilical cord; in place of a halo, her head is surmounted by the placenta. But far from being transgressive, it's a powerfully emotional piece. Neither photograph nor painting, it is magnificently itself.

To 20 Jan (020-7747 2885)