In the early 1850s technical developments and stereo photography combined to revolutionise photographs. During this period clear glass collodion negatives began to replace hazy paper ones and pushed the negative/positive process into the limelight. Glass negatives made it possible to produce multiple positive prints from one highly detailed negative, a massive improvement on the previously popular daguerreotype which was a one-off process. Not only were these new positive prints less likely to fade, but the time needed to take a photo had also decreased making it possible to count exposure time in seconds rather than minutes, increasing the number of things photographers could potentially capture with their cameras. These technical developments coincided with a craze for stereo photography that swept the Western world in the wake of the Great Exhibition held in London in 1851.

From the 1850s right through to the 1870s mounted stereoscopic photographs were immensely popular. It is estimated that millions were made in this period and were so popular they could be hired from shops for evening viewings and circulated the globe as gifts. There was a small lull in their popularity in the 1880s and 1890s but in the early 1900s large companies, like Underwood and Underwood and H. C. White, again began producing silver gelatin and lithographed stereoscopic images on a huge scale right through to the 1920s.

Geoff Barker, Curatorial, August 2009.

References
William Darrah, 'The World of Stereographs', W. Darrah, 1997
Helmut and Alison Gernsheim, 'The History of Photography', Thames and Hudson, 1955

A stereo photograph is comprised of two photographs, one taken as the left eye sees the view and another slightly offset as the right eye would see a view. These photographs are mounted on a card which is then fitted into a viewer. The viewer allows the brain to superimpose the two images, imitating the three dimensional stereovision of the human eye.

Stereo photographs are essentially the combination of two inventions of the 1830s. Sir Charles Wheatstone announced the first of these in 1838; it was an optical viewer that could combine two specially developed three-dimensional drawings that took into account the slight variation between the right and the left eye. The second occurred in 1839 when two different photographic processes, the 'daguerreotype' by Louis Daguerre and the 'Talbotype' or 'Calotype' by Henry Fox Talbot, were announced to the world.

In the 1840s Sir Charles Wheatstone began experimenting with Talbot's process which enabled him to place two slightly offset photographic images in his viewer. The success of these experiments inspired a Scotsman, Sir David Brewster, to announce in 1849 his modification of the stereo format, a portable viewing device called a lenticular stereoscope. It was Brewster's stereoscope which defined the standard for the new format and which was popularised from the early 1850s.

Geoff Barker, August 2009.

References
William Darrah, 'The World of Stereographs', W. Darrah, 1997
Helmut and Alison Gernsheim, 'The History of Photography', Thames and Hudson, 1955, 253

Photograph, mounting for aligning instrument along equator, stereoscopic print, photographer unknown, Sydney Observatory, Sydney, New South Wales, Australia, 1902-1912

A black and white photograph featuring two images (stereoscopic photo format) of a mounting for aligning an instrument along the equator. The mounting is set up on a lawn presumably at Sydney Observatory.

Made: 1902 - 1912

In pencil on the back of the photograph '1/38'.

P3549-97

1902 - 1912

77 mm

152 mm