How a picture gets made is of immediate interest to painters. Practicalities such as pigments, drawing instruments, available light and available models are their concern.
Art historians, on the other hand, tend to regard documentation as vital evidence rather than the paintings themselves. This is why David Hockney's investigations in Secret Knowledge (Thames amp; Hudson pound;35) into the Old Masters' use of mirrors and lenses are so refreshing.
In a profuse, intermittently brilliant book, busy with pictorial case studies and arresting details, Hockney argues that, as early as the 1430s, artists were using mirrors and lenses to achieve certain effects. He demonstrates that a concave mirror could be used as a sort of lens to project images and that in, for example, Jan van Eyck's "Arnolfini Wedding" in the National Gallery, features such as the chandelier behind the glum couple could only have been painted using this device.
The second half of his book is bulked out with research material: accounts of camera obscuras and gadgets such as the camera lucida (a prism on a stick) used as visual aids over several centuries.
It is not exactly a revelation that, for example, Holbein, Ingres, Canaletto and Vermeer were apt to avail themselves of viewing and plotting devices. It has long been assumed that certain forms of precision could only have been achieved using reflection and projection.
Characteristically, Hockney presses further. He insists that to draw people grinning, for instance, you have to avail yourself of some sort of fix-it kit. Cartoonists, I suspect, will disagree. He is on firmer ground when he examines the curious distortions in portraits by Frans Hals and Van Dyck, and the odd angles and amazing foreshortenings that make the works of Caravaggio so cinematic.
But he is persuasive in his overall contention that the development of photography in the 19th century was an end rather than a beginning; and that computerised image manipulation software such as Photoshop has brought the process full circle.
- Picture: a Hockney Polaroid collage