Diagram showing a Wheatstone Stereo Viewer
1:1 Before the Stereoscope
Three-dimensional vision depends on seeing objects with both eyes simultaneously. But there are other perceptual cues which help to suggest depth. Some of these have been applied in two-dimensional art since Classical times. Among these are shading and the relative sizes of objects. Shading produces the appearance of light falling on a three-dimensional object. Diminishing size suggests increasing distance from the viewer, of a person or a tree, for example. Up to the Middle Ages these techniques were not applied with any rigour. Indeed naturalistic representations were seldom an objective of artists before the Renaissance, and relative size of figures may have had more to do with their relative importance in the story being told than any consideration of perspective.
The mathematically accurate construction of perspective scenes was a significant innovation of art in the Renaissance. This was a feature of the works of artists such as Piero della Francesca, who wrote a treatise on perspective in the fifteenth century. From the Renaissance on, perspective was applied when art was intended to be realistic.
By the eighteenth century, prints were being produced in large numbers for private collectors. Among these were perspective views, especially of townscapes, designed for viewing through the zograscope or optical diagonal machine, which was probably developed in Paris early in the eighteenth century. Viewing such prints through a mirror and lens heightened the perspectival effect but did not produce a truly three-dimensional image. This did not come until the researches of the English physicist Charles Wheatstone in the early nineteenth century.
1:2 Wheatstone Discovers Stereoscopy
Sir Charles Wheatstone (1802-1875) discovered the principal of combining two similar images to create the illusion of depth in the early 1830s. Partner in a firm of musical instrument manufacturers – he invented the concertina – and Professor of Experimental Philosophy at King’s College, London, from 1834, Wheatstone was a pioneer of the electric telegraph and the inventor of numerous scientific devices.
Wheatstone invented several types of stereoscope – a name he coined from the Greek words for ‘solid’ and ‘to look at’ – for viewing pairs of images to imitate what would be seen by each eye. He had stereoscopes made as early as 1832 but did not announce his ideas until 1838. The design of stereoscope Wheatstone favoured involved a pair of mirrors at right angles for viewing images on panels facing each other. A commercial example of such a reflecting stereoscope is illustrated here.
In 1838, the production of two similar but not identical images with any degree of complexity presented difficulties. The announcement of the photographic techniques of Daguerre and Talbot in 1839 held the promise of successful stereoscopic images. Wheatstone took an early interest in photography and encouraged several photographers to take stereo pairs of images in the early 1840s. The results were not altogether successful as photography was still in a very primitive state. Photography only developed to a state where it could be practised widely by the early 1850s, and then stereo photography became a phenomenal craze, but not with the reflecting stereoscope.
1:3 Brewster's Portable Instrument
Wheatstone’s reflecting stereoscope being large and cumbersome, Sir David Brewster (1781-1868) devised a smaller, more portable instrument using lenses – referred to as a lenticular stereoscope. Brewster was a scientific editor and writer who was also a leading experimental researcher, especially in optics. He invented an optical toy, the kaleidoscope, which was phenomenally popular in the late 1810s and has continued to be produced. He was also very prone to getting into very public disputes.
Brewster was among those who saw Wheatstone’s demonstration of the stereoscope at the annual meeting of the British Association for the Advancement of Science held in Newcastle-on-Tyne in 1838. He was intrigued by the phenomenon of stereoscopy and soon obtained a reflecting stereoscope. In 1849 he proposed his own design of stereoscope consisting of a box with a pair of half lenses and an opening to insert a ‘slide’ – the pair of images mounted side by side.
Reproduced courtesy of T.K. Treadwell, Institute for Photographic Research, Texas, USA
Brewster was unable to find any prominent scientific instrument maker in Britain to manufacture his design and in 1850 took a prototype on a visit to Paris where he showed it to the optical instrument maker Jules Duboscq. Duboscq began manufacturing lenticular stereoscopes and also taking stereo daguerreotypes. During the Great Exhibition, Duboscq exhibited the new stereoscopes. This was the beginning of the popularity of the stereoscope in the form devised by Brewster. With improvements in photography, especially the introduction of the wet-plate process, stereo photography (and photography generally) became increasingly popular as the 1850s wore on. Over the following decades, numerous variants of the lenticular stereoscope were devised, stereoscopic cameras were invented, and stereoscopic photographs were produced by the million.