Through a Lens Slyly.(David Hockney's theories of painting)

The renowned English painter David Hockney says the a-ha! moment for him came during a visit to a 1999 Ingres exhibition at London's National Gallery. He was looking admiringly at a suite of portrait drawings the French academic master made around 1820. "It was the smallness and the speed of the drawings that got me," Hockney says. He started to wonder if Ingres hadn't used the recently invented camera lucida--a small glass prism that can be attached to the side of a drawing board. An artist looking down through the prism can see a projection of the thing he's trying to draw. "I also blew up a reproduction of one of Ingres's portrait drawings," Hockney says, "and thought, 'My God, that's Andy Warhol's line!' " (Warhol drew by quickly tracing projected photographs, rather than by drawing directly from life.) Of course, to most people tracing is a kind of cheating that reduces fine art to coloring-book activity.

The Ingres epiphany sent Hockney careering off on some manic research that, he says, proved to him the startling proposition that many old masters--from Jan van Eyck in the mid-1400s, through Vermeer in the 17th century, right up to Ingres--used lenses and projections to help them make their realistic pictures. Hockney says, for instance, that it would have been just about impossible for even van Eyck to render accurately the complex chandelier hovering over the nuptial couple in the "Arnolfini Marriage" (1434) without the aid of a lens. But lenses big enough to do the job weren't made until a century or more later. It was simple, says Hockney: van Eyck used a concave mirror (not coincidentally, there's a convex mirror depicted in "Arnolfini") to project an image of it onto his panel.

Hockney's discoveries have resulted in a new book, "Secret Knowledge: Rediscovering the Lost Techniques of the Old Masters," a BBC program on the subject and, earlier this month, a contentious two-day conference in Manhattan. The speakers included passionate opponents of Hockney's thesis, as well as such supporters as University of Arizona professor of optical physics Charles Falco and British theoretical architect Philip Steadman, who see themselves as no-nonsense scientific detectives merely following where the evidence leads. Steadman has written his own book on Vermeer's alleged use of a camera obscura-- literally, "dark room"--in which the painter would work from an upside- down image of something outside the room projected through a lens, or just a pinhole, in the wall. "My argument is strictly from the perspective geometry of Vermeer's paintings," Steadman says. He has built a replica of the room depicted in many Vermeers and photographed it from a camera obscura. The correspondence between his photos and the paintings, he says, is too exact to be coincidental.

The pro-Hockney forces tend to view recalcitrant art historians as turf protectors with vested interests not only in unassisted artistic "genius" but also in their own franchises to interpret it for the public. Says Falco: "Art historians are a closed community which avoids technical issues by saying, 'I'm not going to bring up pinhole lenses if you don't'... If all art historians had been forced to take a one- semester, gently presented course in optics in college, this stuff would have been discovered generations ago." Hockney himself treads a little more lightly: "All I've said is that there was a tool used, and more widely than thought."

Hockney's emphatic detractors include Metropolitan ...