David Hockney's celebrated theory that the Old Masters used mirrors and lenses to construct their paintings has been challenged by a British optics expert.
The suggestion that many of the Renaissance's most cherished works of art were produced through backroom trickery was outlined in a bestselling book - Secret Knowledge - and a BBC television programme.
Mr Hockney, one of the greatest living British artists, argued that the almost photographic quality found in many paintings from 1430 onwards could be produced by tracing over or copying images projected onto canvas or paper. He argued that had been deliberately erased from history.
But delegates at next week's European conference on visual perception, in Glasgow, will hear that the evidence does not stand up.
Christopher Tyler, associate director of the Smith-Kettlewell Eye Research Institute in San Francisco, US, has analysed paintings picked out by Mr Hockney and Charles Falco, professor of optical sciences at Arizona University.
Dr Tyler found inconsistencies that seemed to contradict the theory when reconstructing the perspective geometry that gave each piece of artwork its 3-D quality.
"My evidence implies that Renaissance artists constructed their compositions purely through artistic intuition, without optical aids," Dr Tyler said.
Mr Hockney and Professor Falco's research showed that the lenses available at the time could provide clear projections of only small sections of scenes with a very narrow depth of field.
But Dr Tyler's discrepancies were often within discrete regions or showed an implausible alignment across the whole painting, suggesting that localised projections were not involved.
When he analysed Jan Van Eyck's Madonna in a Church (1438), he found that the perspective of the cathedral interior hid a set of incompatible geometries.
Likewise, two books pictured in Hans Holbein's Ambassadors (1503) possessed a host of contradictory vanishing points, and the lines of latitude of a nearby globe were inaccurate.
From Donatello to Canaletto, Dr Tyler's perspective analysis revealed defects that betrayed varying levels of geometric understanding on the part of the artist but no evidence of optical trickery.
Dr Tyler concluded that many artists such as Andrea Mantegna would have benefited had optical techniques in fact been available.
On a website, Professor Falco rejected Dr Tyler's criticisms as based on him having "an elementary misunderstanding of optical perspective, which in turn directly resulted in his incorrect conclusions."
Martin Kemp, professor of art history at Oxford University, said he was sceptical that optical devices had widespread use in the Renaissance but that Mr Hockney's insights were still both plausible and useful.
Professor Kemp added that Dr Tyler had rewritten Mr Hockney's thesis in order to refute it and was ignorant of Renaissance paintings.