SECRET KNOWLEDGE: Rediscovering the Techniques of the Old Masters
by David Hockney
(Unpublished)

"It could be that the West's greatest mistakes were the 'invention' of the external vanishing point and the internal combustion engine," writes the British artist David Hockney in the concluding paragraph of this remarkable book on the history of painting and the science of optics: "Think of all the pollution from the television and the traffic."

Behind this wry perception of how the real world works lies a breadth of historical vision and an acuity of insight that give a measure of the scope and tone of Hockney's newest investigation into the way we see things-and the way artists reveal them to us. A plain-spoken Yorkshireman who rode the ladder of fame from brash art student at London's Royal College of Art in the late 50s to a rare kind of superstardom for a visual artist, he is known throughout the world in good part for his brilliant images of the world's capital of images, Hollywood, California.

Images, of course, are the artist's stock-in-trade; knowing their hold on the human mind, Hockney has been an outspoken critic of their abuse in the hands of contemporary power-mongers in politics and the media. He has done battle, too, both verbally and visually, with that "external vanishing point" he holds in part responsible for photography's stranglehold on the way we're now conditioned to see the world: the plethora of visual information that constantly bombards us comes in the form of film, television, and print-not to mention cyberspace-all derived from the camera's glassy eye.

By a nice piece of timing, the publication of "Secret Knowledge" coincided with the exhibition "David Hockney Retrospective: Photoworks" at the Museum of Contemporary Art in Los Angeles. Long fascinated with the use of the camera, he began exploring the medium for his own purposes more than twenty years ago, seeking ways to counteract its inherent flaw: "Photography's alright," he once famously said, "if you don't mind looking at the world from the point of view of a paralyzed Cyclops-for a split second." His solution, at the time, was to create "photoworks" by assembling multiple photographs into a single, complex image, involving simultaneously multiple points of view which allowed for expansion of the perceptual experience in space and time.

Seeing the world is what art is all about, for Hockney. His two previous books-the most recent before "Secret Knowledge" was titled "That's the Way I See It"-are narrative records of how his vision developed, and of his struggle to create images that would account for the fullness of the human experience. Never much interested in abstraction, a modernist attempt to address the limitations of painting dominated by a post-Renaissance pictorial obsession with perspective, he has flatly challenged mainstream art assumptions by continuing to champion the image as a creation of hand and eye working in coordination, a product of the human body as much as the brain. Drawing for this master-draftsman is, importantly, "an account of seeing by a human being."

"Secret Knowledge" started when Hockney stopped by to see a 1999 National Gallery show of drawings by the early 19th century French artist Jean-Auguste-Dominique Ingres. "I was struck with how small the drawings were," he writes, "and yet how uncannily accurate. I know how difficult it is to achieve such precision, and wondered how he had done it." On a hunch that Ingres might have used a then recently invented optical device, the camera lucida, to project images and trace those hard-to-capture, fleeting moments like a facial expression or the fall of drapery, he embarked on his own series of portrait drawings using this "prism on a stick." He was soon convinced that he was onto a discovery that led much further back in art history than Ingres. "Vermeer was thought to have used a camera obscura," he observes. "This can be deduced from the optical effects in the paintings. Was he the first, or were there others before him?"

Not one to turn down such a challenge, Hockney embarked on an increasingly excited visual journey through the history of Western art, and it becomes an adventure in itself to follow his agile, sometimes eccentric mind and his inquisitive eye. In his studio, first, laying the ground for his detective work, he put together a 70-foot wall of images, with northern Europe at the top and southern Europe at the bottom, leading from a Byzantine mosaic from Cefalu Cathedral, Sicily, (c. 1150, "pre-optics") to Vincent Van Gogh's "Portrait of Trabuc" (1889, "post-optics.") "My Great Wall," he writes, "allowed me to see, with one sweep of the eye, what art historians have long recognized as a shift towards an ever greater naturalism from the fifteenth century to the nineteenth. But what was immediately apparent, surrounded by so many images, was that this was not a gradual process-the optical look arrived suddenly, and was immediately coherent and complete."

Hockney concluded that from the early 15th century, a variety of optical projection devices must have been available to painters, and used by them, in order to create the effects they were able to achieve. And aware that his theory would be heresy to those with a vested interest in the notion of art as the superb mastery of technical skills-whether historians or traditionalist artists-Hockney began to put together a meticulous case to support his conjecture.

The first and most obvious objection, he allows, is that we would surely have known about the practice long ago, and besides there would be written texts to document it. Hence his argument that it was "secret knowledge," closely guarded by artists with good business sense, in much the same way that corporations guard their secrets today. Think Coca-Cola. Or Microsoft. Then, too, such knowledge could prove dangerous to one's health in a world ruled by dogmatic powers that brooked little dissent, and responded mercilessly to external threat. Think Galileo, whose discoveries also derived from a simple optical device.

The first part of Hockney's book-"The Visual Evidence"-is, if nothing else, an object lesson in how to look at paintings. Given the spectacular quality of today's reproductions, it's a treat to follow a master painter's eye as it bores in on visual conundrums and tasty details, asking not the theoretical but always the practical question: How was it done?

At first, Hockney's evidence seems arguable at best. Isotta Brembati's gown in Giovani Battista Morani's magnificent 1553 portrait is certainly "the most elaborate of dresses, with a bold design that is always believable on its surface, following the folds, and with subtle highlights and shadows all depicted." But why not attribute this to the dazzling skill of the artist, rather than to an optical aid? And how about the awkward, stylized quality of St. George's armor in Andrea Mantegna's 1460 image of the saint? Might it not simply reflect a more primitive level of skill than Antonis Mor's, in his 1557 portrait of Philip II of Spain, resplendent in his almost photographically rendered suit of mail?

But Hockney leads us through the pictures into ever more persuasive arguments. He walks us through the intricate detail of Hans Holbein the Younger's "The Ambassadors" (1533), for instance, "filled with curved and spherical objects, all of which would have been difficult to eyeball"-even for a gifted draftsman like Hockney: a globe with lettering that accurately follows its rounded shape, a perfectly-foreshortened lute, and the trademark Holbein distorted skull-a pun on his name-which Hockney neatly squeezes back into shape for us with a computer. In Lorenzo Lotto's "Portrait of a Husband and Wife," (1543), his eye picks out an odd misalignment in perspective and a focal shift in the pattern of a carpet: "The human eye" he argues, "would not see this, but a lens would."

Offering a page of eighteen portraits, dating from 1430 to 1560-5, each with a window-ledge effect, he points out their remarkable similarity in scale, composition, and lighting, and explains how this curious coincidence of effects could be accounted for quite simply if the artists had used a projection device. His own experiments with pinhole projection in a camera obscura, carefully documented, produced identical effects. Putting together the "window" effect with such anomalies as focal shifts in the Lotto painting, he looks at a Dieric Bouts altarpiece, noting how a chandelier, though hanging above, is seen head on, as are each of the faces, and begins to speculate that even large, complex works could have been produced with the aid of simple optical devices, by stitching together many windows-as he himself had done in the photoworks he called his "joiners."

Once alerted to such subtle shifts, Hockney hones in on visual evidence to deduce changes in optical technology. Having demonstrated how Caravaggio's "Sick Bacchus" (1594) could have been created in four sections, or windows, by the use of a mirror-lens, he turns his attention to the same artist's "Bacchus" of just a year later to suggest a switch from the mirror-lens, which turns projections upside-down but keeps them right way around, to a conventional lens, which reverses the image without inverting it. Noting the anomalous appearance of a large number of left-handers at just this moment in the history of painting, he reverses several images-along with Caravaggio's-to demonstrate how much more natural the pose appears when all these lefties are restored, by the simple magic of the mirror, to right-handedness.

Following up on the visual evidence, Hockney's supporting "Textual Evidence" is a selection of literary, scientific and critical texts from the 10th century through today. Perhaps not surprisingly, it is the briefest section, since there is virtually no written evidence to corroborate his suspicions (that is, if we discount Hockney's little joke-the whimsical inclusion of a torn, faked note, penned, we suspect, by the author himself in a gently mocking satisfaction of the academic need for documentation: "Dear Hugo," it reads, "Could you get a couple of those make-up kits at ye Bruges Mirror Supply Co. My dear Wifee has lost hers. Sworn to Secrecy, Jan." We understand, of course, van Eyck.)

Lacking a smoking gun in the form of artists' notes or writings, however, he cites such early scientific writings as the 10th century Arab scholar Alhazan's "Opticae thesaurus" and Giambattista della Porta's "Magiae naturalis", first published in 1558, to establish that the technology was indeed available; and entries cited from Leonardo's notebooks, along with a famous Albrecht Dürer woodcut of 1525-an actual demonstration of the use of an optical device in drawing-do suggest that artists were familiar with the scientists' work.

A final section, "The Correspondence," begins with letters to the initially skeptical but politely interested Oxford University art historian, Martin Kemp-the author of a major book on "The Science of Art." With Kemp as his main correspondent, Hockney sets out to test his case against the accepted wisdom of art world cognoscenti. Expert demurrals prod him to further research, more examples, and soon his net widens to include other historians and museum professionals, winning gradual, sometimes grudging assent.

Amongst the most compelling of these exchanges is one initiated in March, 2000, with University of Arizona Professor of Optical Sciences Charles Falco. Unlike the art historians, the scientist needed little convincing: "It's absolutely clear to me from the examples you showed me," he writes already in his first letter to the artist, "that you're right about lenses having been used." For Falco, clearly thrilled at the chance to turn his expertise to so unfamiliar a field of study, documentary evidence is beside the point: he offers his own detailed calculations based solely on the optical evidence. His analysis of details not only supports Hockney's arguments, it makes remarkable reading on its own account. How often do you read about f-stop values and focal distances in the study of painting?

There will be many skeptics who read this book, particularly those unwilling to relinquish long and fondly held beliefs about mastery in art-though, as Hockney frequently reminds us, to use an optical device by no means obviates the need for the artist's skillful hand and eye. It took the creative mind of a painter to look beyond accepted ideas, and the analytical mind of a scientist to put his thinking to the objective test. In our rush to specialize and separate the disciplines-artist, historian, scientist-we can easily lose sight of the larger picture.

This is a fascinating, compelling, often entertaining book, and I trust that its reach will not be limited to art historians. A critical understanding of the power of images, the way they are generated, and the way they are used, is of significance to all of us in a society dominated by them, as ours is. The airwaves are indeed polluted. It's time we understood a little more about the way we are persuaded to construe reality.