Arts: Did Ingres use a camera?

After examining Ingres's brilliant portrait sketches and experimenting with a camera lucida, one of our greatest artists considers the secret history of mechanical aids for drawing

What I am about to say is speculative on my part but is based on visual evidence and my experience of drawing. Artists are generally secretive about their methods, especially about mechanical devices such as cameras and photography - not necessarily the same thing, the camera being much older than the photograph. The photograph is merely the chemical invention of how to fix a projected image, and was first seen in about 1839.

I have always deeply admired the drawings of Ingres. I first came across them more than 40 years ago as an art student in Bradford. They were held up as an ideal in drawing: sensitive, full of character and uncannily accurate about physiognomy.

In January I saw the Ingres exhibition at the National Gallery three times, bought the catalogue and, after a little dallying in Paris, returned to Los Angeles. I read the catalogue from cover to cover and noticed that it rarely, if at all, talked about technique. It was fascinating about the characters Ingres portrayed, but an artist might ask another question: how was this done?

I had been intrigued by the scale of the drawings: why so small, almost unnaturally small, for such accuracy? I looked at them and then blew some up on a Xerox machine to examine the line more closely. To my surprise, they reminded me at times of Warhol's drawing - lines made without hesitation, bold and strong - but I knew that essentially Warhol's were traced. Could these have been done the same way?

The faces in the portrait drawings by Ingres have likenesses that one feels are true. Like real faces, each is very different, but likenesses are achieved by the relationship between the eyes, nose and mouth. Mouths are especially difficult to draw and paint (as John Singer Sargent said, "A portrait is a painting with something wrong with the mouth"). The mouths on these drawings were most clearly visible but drawn very, very small. To anyone who has drawn faces from life they seem uncanny. I found myself fascinated by them and kept studying the reproductions.

I now digress. Someone gave me the Taschen complete works of Van Gogh. At $50 it was an absolute bargain. I looked through it and felt at the end that I had had $50 worth of pleasure already, so all that was to come was free. I left the pages open at the great painting, Harvest at La Crau, with Montmajour in the Background. On the left-hand page was a drawing. At first glance the painting and the drawing appeared the same. But then I compared them and realised they were quite different. In the drawing everything seems closer to the viewer than in the painting. I noticed this because I know the effect cameras have of pushing the distance away, as I had been dealing with this in my Grand Canyon paintings. Van Gogh's painting did not seem to have been done from the drawing.

I kept pondering this, and then looked at The Prisoners in the Courtyard based on Dore's engraving made at St Remy in 1890. I looked up the Dore, and got my assistant Richard Schmidt to photograph it and put it on a transparency, the same scale as the reproduction. They fit precisely. The exact outlines, the negative shapes - very precisely. Much too precise for what an artist might call "eye-balling" it. This would mean either that a copy of the engraving, carefully squared up, exists, or that Van Gogh used some other mechanical means. Perhaps in a hospital in St Remy there might have been an epidiascope for lectures or medical diagrams. He might have immediately seen the possibilities of transferring the engraving to his canvas, and I'm sure he would not have hesitated to use this technique. This in no way diminishes the deeply moving painting - it is more interesting than the engraving. To add colour to black and white would have pleased Van Gogh (there is a painting of his mother in the Norton Simon Museum in Pasadena done from a photograph, and Van Gogh mentions he wanted to add colour to this image). So, back to Ingres.

I looked closer and closer and began to think that some mechanical device must have been used here. I remembered many years ago buying a camera lucida: I tried it for a day, found it too difficult to use, and forgot about it. So I asked Richard to nip down to our local art store and buy one - I knew they would have one. I made a drawing of Richard using it. It is a very simple device - quite small, really just a prism, but it enabled me to place the eyes, nose and mouth very accurately. I then drew from direct observation.

It is merely a tool to place positions very precisely. You have still to be extremely observant and skilful with the pencil and only Ingres could make drawings like this. When I first suggested my theory to art historians they seemed horrified, as though this knowledge would diminish the work. Why, I don't know. Who else made drawings as good as these? Ingres witnessed the birth of photography. His rival Delaroche made the statement, on seeing the daguerreotype, "From today painting is dead." He perhaps meant that the hand inside the camera had been replaced with chemicals.

I think the history of photography and painting in the 19th century has yet to be explored. People hide things - trade secrets as it were - but it is interesting to note that Degas, a great admirer of Ingres, was fascinated with photography. Cezanne did not care for Ingres and his work is very unphotographic. It seems to me that there is an interesting story here, and not just about the biographies of the sitters. Delaroche couldn't have foreseen that his remark about photography wasn't going to apply forever. Few people can see that, even today.

The period of chemical photography is over - the camera is returning to the hand (where it started) with the aid of the computer. All images will be affected by this. The photograph has lost its veracity. We are in a post-photographic age. Even in movies this is happening, in Jurassic Park and the new Star Wars. What it means I do not know. There is a deeply disturbing side to all this, yet also a thrilling one. There is a minimum of two sides to everything - and perhaps an infinity of sides; exciting times are ahead.

50 New portraits by David Hockney using the camera lucida will be on show at the Annely Juda Gallery, 23 Dering St, London W1 from 30 June to 18 Sept as part of the exhibition Space and Line. Also included are the pastel drawings Hockney made for his Grand Canyon paintings which are now on show at the Royal Academy's Summer Exhibition until 15 Aug. This article first appeared in the RA magazine