by Mike Ibbetson

Created on: January 04, 2007   Last Updated: May 08, 2007

Self-educated chemist ANGELO SALA (1576 - 1637) discovered that when paper contained powdered silver nitrate it would react with sunlight, causing it to darken. These pioneering experiments with silver salts were a crucial step towards the later invention of photography. He published his findings in a pamphlet in 1614. Sala's conclusion on the subject was in contrast to Robert Boyle's incorrect theory that the paper darkened due to contact with air.

JOHANN HEINRICH SCHULZE (1687 - 1744) was a German professor at the University of Altdorf. He was the first person to produce Photograms, which were created by using paper masks in direct contact with a jar containing a mixture of silver nitrate powder and chalk. Schulze proved that the darkening of silver nitrate was caused by light and ruled out the possibility of the change being caused by temperature, by observing no tonal change to silver nitrate when heated in an oven.

Englishman THOMAS WEDGWOOD (1771 - 1805), son of famous potter Josiah Wedgwood, made good ground creating Photograms and recording images from his Camera Obscura (or pinhole camera, as we would now call it). He worked along side his friend, assistant and one of English history's most important chemists, SIR HUMPHREY DAVY (1778 - 1829). However, they were never to overcome the problem of "fixing" the image and therefore the prints produced had to be viewed for very short periods of time in a darkened environment.

The French inventor JOSEPH NICEPHORE NIEPCE (1765 - 1833) was the first man to produce a permanent photographic image. In 1826 he was to pull all his research into the process he called "Heliography". This consisted of capturing the light in his Camera Obscurer on a pewter plate coated with bitumen of Judea. After the day-long exposure, the parts of the plate that were exposed to light had hardened. The latent image (of the view from his workroom window) was then revealed by washing the plate with a mixture of white petroleum and lavender oil, to rinse away the soluble, unexposed areas of the plate.
The Heliogram took a very long time to produce, especially in comparison to modern film or digital photography. We should consider ourselves very lucky today, as we learn that Niepce' first photograph required eight hours of exposure. This long exposure time made portrait photography impossible due to the length of time the subject would have to be still.

Frenchman, LOUIS JACQUES MANDE DAGUERRE (1787 - 1851) was a successful commercial theatre

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