The right frame of mind: The work of sculptors Julian Opie and Richard Wentworth starts with a photograph. Then they see how things develop. Iain Gale reports

Turner called it 'the death of art'. But he was wrong. Ever since Louis Daguerre revealed his discovery in January 1839, the camera has been the artist's friend. For the Impressionists, as for Degas and Manet, it provided the scientific basis for a new approach to composition. For the Nabis - Bonnard and Vuillard - it was a clue to the randomness of everyday life. Through its objectivity the Surrealists were empowered to transform this randomness into a low-life picturesque. More recently it has been used by the artists Julian Opie and Richard Wentworth, currently showing in London, in their quest for the signs and symbols of a universal human language.

While Opie uses the camera to distance himself from reality, with Wentworth it is the starting point for still-life memento mori - subtly camouflaged indicators of the ways in which we muddle through the complexities of the post-modern world. Wentworth's theme is human ingenuity in overcoming the little obstacles of everyday life, and the photographs he takes before starting work on his sculptures capture this: the table balanced on the cigarette packet, the finished-with plastic cup pushed into the gap in the wall.

'It's human 'agency',' says Wentworth. 'People don't often realise that. They see it as a 'lower order' of behaviour.' Like such pioneers as Surrealist role-model Eugene Atget, who wandered through Paris photographing the tawdry beauty of the tailor's dummy and the shop sign, Wentworth is rarely without a camera. But unlike the Surrealists he does not seek out his images. 'They have to be encountered. I make sense of them afterwards when I start realising that they are linguistic and 'transcultural'. What somebody does to keep the door open in Vietnam is the same thing someone will do in Ottowa. I'm trying to suggest there's an undertow that we're all part of, and that the various levels of our own internal decorum allow us to use it or not to use it. Some people are excruciatingly embarrassed if there isn't a lock on the lavatory door, but others wouldn't use it if there was one. Everything is in a kind of ballet of organisation. There's a procedure when the traffic lights go down - an incredible ballet of communication.'

Wentworth is intrigued by such schemes, which transcend the ordinariness of created rules. To find them he has embarked upon a 20th-century grand tour. Echoing the 18th-century dilettantes who would gather sketches of ruins to re-create them - bastardised - on the grounds of their estates, he appropriates the historical detritus of modern man to create his own monuments to the passing of time. When making a sculpture, Wentworth does not refer directly to his photographs. 'They're absolutely not aide-memoires. I don't consult them directly. It's a digestive process, in the same way that our complexion has to do with what we eat.' Having appropriated the object as a photographic image, Wentworth hands it back - re-objectified by the mediation of the artist's vision.

Julian Opie is also concerned with the power of the camera to re-make an image. He knows that simply by framing an object in the view-finder we capture it. 'Framing is the first stage in picturing. To point at something and to frame it, immediately makes it into language. I'm always looking around for examples of structures I can use. When I started taking photographs I didn't really know why, but I knew there was something there I could use. That's like language: finding a word that stands for an object or an action that other people recognise. When you photograph something you feel you've 'dealt with' it in a very basic way. This tourist impulse to move on quickly interests me. A lot of the drive to make art is that same tourist sense that you've somehow got to deal with what excites you.'

Opie uses his photographs in the same way as he once used working drawings (which he has described as 'a way of thinking on paper in a language as immediate as writing'). 'Whereas I used to draw before making a work, now I generally photograph some group of things. I don't often look at them. They're a way of focusing on things, listing things in my mind; a way in. My works aren't based on found objects. They're based on codes of recognition. We all have a common agreement that in some sense places - like motorways or airports - don't exist. In the painting Imagine You Are Driving I was just photographing things from the car and I ended up shooting straight ahead. But no one's ever stood in the middle of the motorway. That makes it a very strange place.'

Opie, who thinks of himself as 'a landscape artist', invites comparison with an earlier artist with an interest in photography. At his death, the studio of Camille Corot contained some 300 photographs, many of which were undoubtedly landscapes by his friends Constant Dutilleux and Adalbert Cuvelier. The halation of their chemical process steeped these photographs in twilight and it is no coincidence that Corot's late landscapes, his 'souvenirs', should possess just such a dreamlike quality. It was photography that enabled Corot to achieve his aim, to create landscapes of the imagination which would tap into mankind's collective memory of a golden age. Similarly, Opie's archetypal castle constructions and motorway paintings reach into a universal consciousness.

Both Opie and Wentworth, like Corot, recognise the importance of the camera not, as Turner had predicted, as a short- cut to perfection, but as the unique source of inspiration suggested by Dutilleux in 1854. A photograph, Dutilleux said, 'should only be an interpretation in which the artist brings to bear his knowledge, his skill, but above all his temperament, his own ideas and inner responses; his feelings]'

Richard Wentworth, Serpentine Gallery, London (071-402 6075), to 3 January.

Julian Opie, Hayward Gallery, London (071-928 3144), to 6 February

(Photographs omitted)