I took this stereographic photograph from my bedroom window when I was twelve years old, living at Mapesbury Road in London in 1945. We lived at number 37, and the view was of the junction of Exeter Road and Mapesbury. I moved the camera between the two exposures a couple of inches – about the same distance as that between my eyes. To create such an image you don’t want any movement. You can do this only with a static scene, otherwise you have to use a stereoscopic camera with two lenses. There were stereoscopes in the house for viewing stereo pictures, but I just had a regular camera, which I would move into the right positions between each picture. In order to process the images into a stereo anaglyph, I remember that one used this light-sensitive red and green paper, the Carbro process. Then one would view the anaglyph with a special pair of stereo glasses, like the red and green ones we sometimes used in the 3D cinema.

Stereoscopy has been very much on my mind again recently. In the 1890s William James imagined the apparent continuity of consciousness to be like a zoetrope or a motion picture – a rapid sequence of frames or stills, fused together by the mind. I have been intrigued by certain neurological states where the normal continuity of vision breaks down, and one can see a series of stills. This can sometimes happen with a migraine, or with various drugs – LSD, for example. About five years ago, I was fascinated when Francis Crick and Christof Koch published a theory of visual consciousness, in which they proposed what they called a ‘snapshot hypothesis’. In fact, various pieces of evidence now suggest that visual awareness may consist of a series of stills which are somehow fused together in the zoetrope of the brain or the mind. (The history of neurology and psychology often uses such mechanical and often photographic metaphors.)

Crick and Koch’s theory is still being considered. Stereo is again a hot subject, as are colour and motion – three things which were being explored in Victorian photography. Of course these were being examined long before then. For example, Thomas Young formed his three-colour hypothesis in 1801, and this was very much in James Clerk Maxwell’s mind when he did his three-colour separation photographs in the early 1860s.

I think one of the things that attracted me to photography as a boy, and again now at the physiology end, was that these basic methods made one wonder how the brain worked. I still think stereoscopy is miraculous, in a way. I know at one level that there is a computation by the brain, but computation is one thing and consciousness is another.