Controversial methods For more than a hundred years, it has been suggested that the great 17th-century Dutch master Johannes Vermeer made use of the camera obscura as an aid to painting. The camera obscura was the predecessor of the photographic camera, but without the light-sensitive film or plate. It is well established that in the 18th century some other famous painters employed the device, the best-known being Canaletto, whose own camera obscura survives in the Correr Museum in Venice. The English portrait painter Sir Joshua Reynolds owned a camera; and the device was widely used by landscape artists, both professional and amateur, up until the invention of chemical photography in the 1830s. With Vermeer the question of whether he used optical methods is more controversial. The camera obscura was the predecessor of the photographic camera, but without the light-sensitive film or plate. The term 'camera obscura' means 'dark chamber', because the instrument up until the 16th century typically took the form of a closed room, the windows shuttered, with a small hole in a blind or door. Light entering the room through the hole then cast an image onto a screen or onto the wall opposite the door. One problem is that the image in such a 'pinhole' camera, even of a sunlit summer landscape, is very dim. The one object that is clearly visible is the sun itself. Indeed this remained the only real application of the camera up until the 1550s: for astronomers to make solar observations without damaging their eyes. The first published illustration of a camera (of this or any type), is in a book from 1545, by the Dutch mathematician and astronomer Gemma Frisius. It shows an eclipse observed by Gemma Frisius at Louvain in the previous year. The situation changed in the mid-16th century, when it occurred to a number of people, it seems simultaneously, to substitute glass lenses for simple pinholes. Typically these were convex lenses of the kind then in wide use for the correction of long sight. Two Venetian authors, for example, give clear descriptions of cameras with convex lenses - Daniele Barbaro in 1568 in a perspective manual for architects and painters, and GB Benedetti in a mathematical text of 1585. These authors describe how to draw from the camera image by tracing outlines onto the paper screen. Others even hint at the possibility of laying down colours over the projected image, although this idea is problematic. (How could you see the colours of your paints in the darkness of the closed room?) Top

Camera Obscura An image of a cubicle-type camera, with a lens, was published in The Great Art of Light and Shadow by the Jesuit polymath Athanasius Kircher in 1646. It is a rather eccentric diagram, but the principle is sound enough. In this design the image is projected onto a translucent screen, made perhaps of oiled paper or ground glass, and the artist looks at it on the far side of the screen, away from the scene - an arrangement first suggested by Leonardo da Vinci. This has the advantage that the user does not get in the way of the light. Most of the literature of the camera obscura available when Vermeer was working, in the third quarter of the 17th century, describes instruments that took the form of closed rooms, tents or cubicles (like Kircher's design), which the user worked inside. It has sometimes been suggested that Vermeer might have used a camera of a rather different kind, which certainly existed in his time, but which was only manufactured in large numbers in the 18th and 19th centuries, and which took the form of a closed box, with an external translucent screen. The observer is now outside the box, not inside it. Both Canaletto's and Reynolds's cameras were of this type. One problem compared with the room-type camera is that the image is viewed under ambient light and so seems subjectively less bright. Fox Talbot and the French pioneers of photography, Niépce and Daguerre, built the first photographic cameras by modifying commercially produced camera obscuras of this general type. Why have people imagined that Vermeer might have been a camera user? There is absolutely no documentary evidence to support this idea. The only source of information is the paintings themselves. The first person to make the suggestion, as long ago as 1891, was the American graphic artist Joseph Pennell, who pointed to what he called the 'photographic perspective' of Vermeer's Officer and Laughing Girl. The two figures sit very close across the corner of the table. But the image of the officer's head is about twice as wide as that of the smiling girl. The perspective is perfectly correct in a geometrical sense: the discrepancy arises because the viewpoint of the picture is close to the soldier. We are quite familiar today with foreground objects appearing very large in snapshots. But in 17th-century painting this is rather unusual, and Vermeer's contemporaries would have made human figures in a composition of this kind much more nearly equal in size. Top

Vermeer's techniques A second reason for suggesting that Vermeer used the camera obscura has to do with the maps that he shows hanging on the wall in a number of paintings. These are real maps, printed on sheets of paper that were pasted together onto canvas backings. The art historian James Welu has identified all of Vermeer's many maps and globes, and found surviving examples in museums and libraries. If you look at an actual copy of the map of Holland shown in Officer and Laughing Girl, it is immediately obvious that Vermeer has copied it extremely faithfully - but was this done through the use of a camera obscura? The instrument was used very widely in the 18th and 19th centuries - before photography - for copying prints and pictures, and for enlarging or reducing them - did Vermeer use one in the 17th century? It should be acknowledged that Vermeer could have obtained his 'photographic perspective', and exact reproductions of the maps, by a number of methods other than tracing camera images. Scholars have however pointed to effects in Vermeer's canvases that seem to carry more distinctive marks of an optical way of working. For example, it is significant that there are several passages where Vermeer seems to paint in very soft focus, as in his little portrait of the Girl with a Red Hat. Notice the sculpted lions' heads, which we know from other paintings are decorations on the backs of chairs. Vermeer has a very characteristic way of showing highlights on reflective surfaces like pottery, polished wood or - in this case - polished brass. In reality a highlight takes the shape of the light source that it reflects. Since Vermeer is painting indoors, the sources of light would be the windows; and so the resulting highlights would in reality be rectangular in shape, perhaps distorted into four-sided shapes with curved edges where they are formed on curved surfaces. Here, however, Vermeer has tended to paint the highlights on the lions' heads as true circles. It has been suggested that what he is doing is imitating accidental effects of slightly unfocussed optical images. Top

Visual evidence What happens is that the lens spreads bright points of light into so-called circles of confusion. Such effects would not be seen by the naked eye. The art historian Charles Seymour and the photographer Henry Beville have tried to reproduce these effects, by photographing a similar decorative lion's head in a slightly unfocussed plate camera, with some convincing success. Several authors, including Seymour, have argued that Vermeer painted this and another tiny portrait, Girl with a Flute, using a box camera. The sizes of both pictures are of the order of size of a typical box camera's screen. The present author published new evidence of a different kind in Vermeer's Camera, in 2001. The book describes an analysis of the three-dimensional geometry of the rooms depicted in some of the Vermeer's paintings, made by - so to say - working the normal procedures of perspective drawing backwards. It turns out that ten of the artist's interiors show scenes set in what is, in architectural and geometrical terms, the same room. The scale can be determined with precision in every case from the real objects that Vermeer includes - not just the maps, but also the musical instruments, and two recognisable designs of chair (one of them the lion's head design), examples of which can be found today in Dutch museums. The position of the back wall of this room - behind us, the viewers, and behind Vermeer as he painted - can be fixed from its reflection in a mirror seen in The Music Lesson. The precise position of Vermeer's viewpoint can be determined for each of the ten paintings. Everything that is visible in one painting must be contained within a 'visual pyramid' - a pyramid on its side - whose apex is at the painting's viewpoint. It is possible to determine the positions of the sloping lines that form the edges of this pyramid. Suppose that these lines are continued back, through the viewpoint, to meet the back wall of the room. They define a rectangular area on that wall. The book's key finding is that, in at least half a dozen cases, this rectangle is precisely the same size as the corresponding painting. Top

Vermeer's room This very curious result can hardly be due to chance. The interpretation made in the book is that it is a consequence of Vermeer using a simple booth-type camera obscura, with which he projected optical images onto the back wall of his room. His canvases are the same size as these images, because he has traced them. These findings were made, as described, through a graphical analysis of the pictures' perspective geometry. They were also tested, in effect, via a second route, through the building of a reduced 1:6 scale model of the room, with which it was possible to make photographic simulations of several paintings, and investigate further questions of colour, light and shadow. The book has managed to win over many art historians, including some who were previously extremely sceptical about camera obscura theories. A small core of Vermeer specialists remains, however, to be convinced. Top

Find out more Books The Camera Obscura: A Chronicle by JH Hammond (Adam Hilger, 1981) Vermeer by L Gowing (Faber, 1952) The Science of Art: Optical Themes in Western Art from Brunelleschi to Seurat by MJ Kemp (Yale University Press, New Haven, Conn., 1990) 'Dark chamber and light-filled room: Vermeer and the camera obscura' by C Seymour Jr, Art Bulletin 46, 1964, pp.323-31 Johannes Vermeer edited by AK Wheelock, catalogue of an exhibition held at the National Gallery of Art, Washington and the Mauritshuis, The Hague (Yale University Press, New Haven, Conn., 1995-6) Top