Science backs Old Masters versus Hockney in 'tracing' row

Historians hit back at David Hockney's claim that Renaissance artists used optical instruments to create their masterpieces

Controversial claims that Leonardo da Vinci, Rembrandt and other great artists "cheated" by resorting to optical drawing aids have been dismissed by international scientists.

Controversial claims that Leonardo da Vinci, Rembrandt and other great artists "cheated" by resorting to optical drawing aids have been dismissed by international scientists.

David Hockney, the leading British painter, has split the art world with his theory that prominent Renaissance artists employed a battery of devices such as the camera obscura to help them create their masterpieces, instead of drawing freehand.

Hockney's book Secret Knowledge infuriated traditional art historians, but it topped the bestseller list for weeks and formed the basis of television documentaries in Britain and the United States.

He claims that from the 1420s onwards, artists used mirrors, lenses and the camera obscura (which creates shadow images through a pin-hole or small lens). Images were projected on to canvas which the artists then traced - assisting in the development of realism and perspective.

Now, though, a scientist and art historian at Stanford University in California has produced computer analysis showing that in key instances the claims cannot be true.

Dr David Stork says that, for example, Georges de la Tour could not have achieved the dark, shadow-filled Christ in the Carpenter's Studio (1645) using lenses unless there had been full natural light or many hundreds of candles. Yet computer analysis of the light and shade shows that this could not have been the case.

Dr Stork, a prominent critic of Hockney's theories, said: "What really gets my goat is that the documentaries that came out at the time presented Hockney's findings as having been proved. They just weren't."

Last week the British artist got a further battering from German historians. Hockney claimed in his book that the final version of Jan van Eyck's 1435 portrait of Niccolo Albergati was almost certainly copied from an original sketch using a lens. But the Dresden Museum of Prints believes that unexplained pin-pricks in the canvas show that Van Eyck probably used an old- fashioned pair of compasses.

Brian Sewell, art critic for the London Evening Standard, is not surprised by the findings: "Secret Knowledge is one of the most dangerous books in the last half century. I'm appalled that the art students I regularly correspond with have swallowed his thesis hook, line and sinker. It was only published because of David's popularity, not the quality of the scholarship."

But Sir Roy Strong, former director of the National Portrait Gallery, said: "These academics love controversies - it's what keeps them in work. The fact is that the use of optics doesn't detract from the skill of the old masters. Holbein sometimes used lenses to paint miniatures, but he was also a genius with total visual recall."

David Hockney remains unimpressed by the criticisms. He said: "They're nit-picking. The pin pricks could be a form of notation that Van Eyck was using. As for Stork, he's a scientist who has made a career out of criticising my ideas. He's milking it for any publicity he can get. It doesn't undermine what I'm saying.

"I am a bit surprised that people have gotten so carried away with it all." He will shortly be publishing a paperback version of his book.