Did Renaissance painters 'cheat' with optical aids?

29 March 2010

IT IS one of the most provocative suggestions in art history: did some Renaissance artists use lenses or mirrors to help them paint more accurately? Analysis of a 16th-century artwork dubbed a "Rosetta stone" for optical techniques suggests they did.

The theory that Renaissance artists used optical projection was proposed in 2000 by artist David Hockney and optical scientist Charles Falco of the University of Arizona in Tucson. Most art historians have yet to be convinced.

The first actual records of artists using optical techniques came when German Jesuit scholar, Athanasius Kircher described them in 1650. Dutch painter Jan Vermeer may have used a pinhole to project images onto canvasses, although there is no proof he used this for painting.

Falco and Hockney claim to have spotted the signature of optical projection, perhaps using a concave mirror, in a painting created more than a century earlier. At the American Physical Society (APS) meeting in Portland, Oregon, last week, Falco presented detailed analysis of Husband and Wife, a 1525 work by Lorenzo Lotto (pictured). "We call it the Rosetta stone because we got so much information from it," says Falco.

The pair argue that distortions in the oriental carpet match what would be expected if Lotto had projected the image, traced out part of it, then moved his mirror twice to bring two other portions of the carpet into focus. For example, there are multiple vanishing points, suggesting it was painted from different perspectives (see diagram). What's more, he points out that the back of the octagonal pattern is blurred, as if traced out of focus.

At the APS meeting, Falco also presented images of the painting taken using an infrared camera. Beneath the red paint of the carpet, he found a region of neat sketch lines, a region of hazy lines, and a region of no lines. These correspond to the three regions he and Hockney think have been painted with different focuses. Falco believes the decline in the quality of the sketch lines reflects Lotto's struggle to keep the pattern on the carpet coherent after changes in focus, which would also have slightly altered the magnification of the image.

Optical scientist David Stork of Ricoh Innovations in Menlo Park, California, remains sceptical. Stork says that as the red paint covers the sketch lines, they could not have been seen when Lotto was painting the geometrical pattern on top, making them irrelevant. "This evidence is consistent with traditional, non-optical explanations," he says.