# The Mystery in the Mirror - Page 3

## Philip Steadman's Discovery

Philip Steadman is Professor of Architectural and Urban Morphology at the Open University in the UK. An architect by training, he became interested in this old question, but approached it from a new direction, through the perspective geometry of Vermeer's paintings. For a start, many of the paintings seem to show the same room. Certainly the same architectural features seem to recur: the characteristic pattern of leaded panes in the casement windows, the black and white marble tiles on the floor, and, where the ceiling is visible, the same size and spacing of ceiling joists. We might suppose that this was an actual room in the house belonging to Vermeer's mother-in-law Maria Thins, where Vermeer and his wife lived after they were married. The site of the house is known, but it was demolished in the 19th century.

The technique that Professor Steadman used (which is first described by Leonardo) is esentially that for setting out a frontal or one-point perspective, but carried out in reverse. The straight lines of the architecture receding away from the viewer all converge together in the picture to the central 'vanishing point'. This establishes the level of the 'horizon line' which passes through this vanishing point.

The other diagonals of the pattern of floor tiles also converge together and meet at two points on the horizon line, the so-called 'distance points'. The distance from the vanishing point to either of the distance points must be equal to the theoretical viewpoint of the picture from the picture plane. In other words, this is the distance you should place your eye from the picture, in order to see the same view as the artist did.

From the height of the vanishing point in the picture it is possible to compute the height of the actual viewpoint above the floor in the room. From all this information it is possible to work out more-or-less complete plan and side views of the room and the furniture. But this only gives the *relative* sizes of the various features of the room, not the absolute scale. We could be looking at a representation of a doll's house populated with very small people, or a very large room filled with giants. Except that objects in the room, like the maps on the back wall, and in one case a painting hanging on the wall within Vermeer's painting, do give an exact scale for the room, since these objects still exist, and therefore we can work out the dimensions of the walls, the height of the people, and so on.

This reconstruction of the room in three dimensions is useful up to a point, but doesn't prove anything either way about the possible use of a **Camera obscura**. Professor Steadman's next step, which he came upon partly by chance, was however quite extraordinary, and this is where dramatic new light has been thrown onto the working methods of Vermeer. The clue lay in the image in the mirror...

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