Of all the great art galleries in the world, the National Gallery in London has proved one of the last to either embrace photography as a branch of art or as a fit subject for exhibition. Which makes its first proper show of the relationship between photography and the Old Masters, opening next week, something of an occasion. It joins, by coincidence, a veritable host of other photographic exhibitions at the present, Davidson, Eggleston and others from the Sixties and Seventies at the Barbican, William Klein and Daido Moriyama at Tate Modern and Hiroshi Sugimoto at Pace in London, with Henri Cartier-Bresson and Ansel Adams to follow at Somerset House and the Maritime Museum, next month. Rarely can an audience be quite as well provided for as London at the moment.
The National Gallery may be late on the scene but its timing could hardly be bettered. With photography increasingly recognised as an art in its own right, prints from the original negatives by well-known photographers regularly sell for £5,000 or £10,000 each. When limited-number prints from big names such as Richard Avedon are concerned, the sums leap to as much as £500,000 and, in the case of the German photographer Andreas Gursky, between £3m and £4m, as museums compete with modern-art collectors for the privilege of owning iconic images of our time.
Photography has always vied with painting for a position as a fine art in itself. What the National Gallery is now seizing on – quite rightly – is the development in the last decades of an art photography which deliberately looks back to the high art of the past and the Victorian pioneers of photography as its model. Large in scale, often monumental in intent, the works now form a genre all of their own. Placing them side by side with their forebears makes a wonderful exhibition.
Why art photography should have developed in this way is an open question. It has a lot to do with advances in technology which have enabled artist photographers to size up their deep single shots into life-scale and to control the colour and the textures in printing. The best photographers have always taken care of the printing process but we now have a generation that uses technology as painters have traditionally used the brush, to refine, to elaborate and to deepen the effect. It goes deeper than this, however. Over the last 30 years, and even more in the aftermath of 9/11 and the midst of recession, there is a retreat from post-Modernism, with its obsession for irony, jokes and a multi-faceted approach to art, to something much more detached and classical. Just as many artists after the wars of the last century stepped back to a kind of cool abstraction, so many artists today are searching for a kind of melancholic sobriety, a sense of the frozen moment which photography is uniquely able to provide.
Which is where photography entered in the first place. From early on the young discipline saw itself as a form of art and contender with paintings for seriousness. The major figures of the Victorian period – Julia Margaret Cameron, Roger Fenton, Oscar Gustave Rejlander, Gustave Le Gray and the others represented in the National Gallery show alongside their painting models and their modern imitators – quite consciously sought not just the dignity of art but its moral thrust. Cameron, in particular, during the late 1860s and early 1870s walked hand-in-hand with the Pre-Raphaelites and the art of her time in an effort to combine realistic detail with ethereal sentiment. Place her portraits, as the exhibition does, side by side with the paintings of George Frederic Watts and you see precisely the same purpose.
So with the still lives of Roger Fenton and other photographers of the mid-19th century, which aim to replicate both the glowing realism of 17th-century painters but also their indications of decay and the fragility of beauty. Look at the seascapes of Gustav Le Gray from the 1850s and you see an artist reaching out to portray the sublime in the way that Turner was doing.
With nudes, of course, the realism became a problem. While photographers such as Rejlander bathed their photos in the aura of classical statues and the painting of Ingres and Botticelli, the photograph gave the female form a living reality which shocked some and excited others. Art and pornography merged in a way that even the most erotic works of Velazquez and Goya could never have.
And it was the truth of the real which took photography away from art in the last century to pursue its own courses in the photojournalism made possible by the 35mm camera, in the avenues opened up by magnification and skewed viewpoint and in the colour film introduced in the 1930s. For most of the 20th century, photography didn't vie with painting or refer back to it. It felt it was itself the art of modernity with no need for a backward or even a sideways look.
The radical thing about the contemporary photographers assembled by the National Gallery is not just that they look backwards to the traditions of painting and early photography for their models, but they do it by glorying in the realism which makes photography unique. Their works ranges from the masters of the monumental such as the Canadian Jeff Wall and the German Thomas Struth to the more intimate studies of bathers of Rineke Dijkstra from Holland and the exploding still lives of Ori Gersht from Israel.
Wall famously showed his life-sized narrative picture The Destroyed Room, based on Delacroix's The Death of Sardanapalus in the form of a negative, back-lit, in a gallery window in 1978. Struth makes his pictures as large but they are of scenes in which the people are dwarfed by the space so that the viewer both looks on and in. Sarah Jones enlarges her pictures of flowers to three or four times life-size so that every detail is shown and the whole given huge presence. Dijkstra sharpens the detail of her life-size pictures of bathers by using fill-in flash photography. Richard Learoyd employs plain, neutral backgrounds and suffused lighting to give his figures sculptural presences.
Magnification on this scale has the effect of bringing the viewer directly into the picture as much a participant as an observer. It encompasses the viewer as she or he stands before it. The heightened realism only adds to the effect. Where painters had to work up their paintings in layers and in meticulous detail, the photographer has realism at his or her instant disposal. The drawback of having to complete in a single shot rather than being able, like a painter, to keep returning to the canvas, is turned to advantage. The subject is caught in a moment that, properly composed, communicates something beyond the face or the landscape that is presented. They become faces in your face, impossible not to be gripped by.
The National Gallery exhibition is only part of the story, of course. Where the contemporary artists in its survey of "photography past and present" are bent on bettering the photographic process by imitating painting, other artists are bent on bettering the painting process by drawing in photography. The history of contemporary art, indeed, could be written in the way in which painters, following the lead of Gerhard Richter and the example of the Pop Artists, have incorporated photography into their creative process and how photographers, learning from modern painters, have pushed their craft away from realism into the realms of abstraction. Photography and painting, which seemed to go their separate ways through most of the last century, are now, thanks to Richard Hamilton, Gerhard Richter, David Hockney and many others, now merging.
Anyone interested in the uses of digital photography in art and the possibilities opened up by inkjet printing need only slip within the National Gallery to the Sunley Room to see the late Richard Hamilton works, in which the artist both pays homage to the past masters and grapples with the challenge posed by the realism of modern reproductive technology. What fascinated Hamilton, as it has intrigued Hockney, is the extent to which digital enables the painter to compose and sketch graphic work and, in the printing, to achieve hyper-realistic effects of colour.
Go to almost any show of a contemporary artist and what you are likely to see is he or she adopting the technology of photography, and often its language, to express their conceptual art. At Dulwich Art Gallery, the contemporary artist Clive Head has installed across one wall of a room of Nicolas Poussins, a large scale painting of a rail terminus. Part of his From Victoria to Arcadia, it is a painting of the most precise detail but also of unnerving space, a narrative of passengers and anonymity based on photographs of Victoria tube station but composed and painted with a traditional eye.
It has been colour as much as anything that has really brought art and photography together. In the era of black-and-white, the photographer reigned supreme in his own field. Ansel Adams, whose photographs of water and the sea go on display at London's Maritime Museum next month, showed that photography could achieve in detail and in depth the sense of the sublime in nature which painters had so long sought, and in its own way do it better. With faster film and lighter cameras, photography became the means of commenting on the human condition and on events in a way which painting seemed too contrived to compete. The photographers on display at the Barbican's current show of pictures of the 1960s and 1970s barely gave traditional art a passing glance as they sought composition in what Cartier Bresson called the "decisive moment".
As the techniques of exposure and printing improved, so photographers became more "arty" themselves. Just a few hundred yards along Piccadilly from the National Gallery's show you can see the seascapes of Hiroshi Sugimoto – to me the finest art photographer of our day – hung alongside Mark Rothko's late dark abstracts at Pace's new Mayfair Gallery. While at one in horizontal composition, they are quite different in texture. Where Rothko works in paint, building it up layer by layer to achieve his effects, Sugimoto is all about light and exposure. Rothko encloses his pictures firmly within the frame, Sugimoto's studies of the sea's horizon seem to extend way beyond the frame into infinity. Both are alike in their ambition to make their separate forms reach beyond representation into the absolute.
At the opposite end of the spectrum of scale, Daido Moriyama, on show at Tate Modern with William Klein, blows up the close-ups of tights and lips to create works of abstract force but human and erotic resonance. What the painter has to do with imagination, the photographer can do by the magnification of detail. Ansel Adams did it with trees, contemporary photographers do it with the stuff of urban life.
Colour, introduced to film in the Thirties, changed things, as an exhibition due next month at Somerset House hopes to show. For purists such as Cartier Bresson it was a dilution of the realism of black and white photography. But for painters it took photography into the glossy surfaces and hectic pace of the new consumer world. With it, photography joined advertising, colour magazines, flashy billboards and brightly-coloured plastic. It was the world in which the old distinctions between genres had no place. All could be used as one in the portrayal of life.
And yet there remains something distinct about photography, in its realism and in its relationship with the viewer. Go to any exhibition and you will see people, young and old, responding without self-consciousness to the picture before them. There's something about the reality of photographs that needs no explanation. Which is why so many painters are now incorporating it into their works.
Seduced by Art: Photography Past and Present, National Gallery, London WC2 (020 7747 2885) 31 October to 20 January