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The necessary first breakthrough in photography was in a different, not eye-centered area : that of making permanent photographic images. Employing data from the researches of Johann Heinrich Schulze : who, in 1727, discovered that silver nitrate darkened upon exposure to light : Thomas Wedgwood and Sir Humphry Davy, early in the 19th cent., created what we now call photograms. These were made by placing assorted objects on paper soaked in silver nitrate and exposing them to sunlight. Those areas of the paper covered by the objects remained white; the rest blackened after exposure to the light. Davy and Wedgwood found no way of arresting the chemical action at this stage, however, and their images lasted only a short time before darkening entirely.
Photography's basic principles, processes, and materials were discovered virtually simultaneously by a diverse group of individuals of different nationalities, working for the most part entirely independently of one another. The results of their experiments coalesced in the first half of the 19th cent., creating a tool for communication that was to become as powerful and significant as the printing press. Four men figure principally in the establishment of the rudiments of photographic science.
The French physicist, Joseph NicEphore Niepce, made the first negative (on paper) in 1816 and the first known photograph (on metal; he called it a heliograph) in 1826. By the latter date he had directed his investigations away from paper surfaces and negatives (having invented, in the meantime, what is now called the photogravure process of mechanical reproduction) and toward sensitized metallic surfaces. In 1827 Niepce had also begun his association with Louis Jacques MandE Daguerre, a French painter who had been experimenting along parallel lines. A partnership was formed and they collaborated until Niepce's death in 1833, after which Daguerre continued their work for the next six years. In 1839 he announced the invention of a method for making a direct positive image on a silver plate : the daguerreotype.
Daguerre's announcement was a source of dismay to the English scientist William Henry Fox Talbot, who had been experimenting independently along related lines for years. Talbot had evolved a method for making a paper negative from which an infinite number of paper positives could be created. He had also worked out an effective although imperfect technique for permanently "fixing" his images. Concerned that he might lose the rights to his own invention, the calotype process, Talbot wrote to the French Academy of Sciences, asserting the priority of his own invention. He then lost no time in presenting his researches to England's Royal Society, of which he was a distinguished member.
All three pioneers, Niepce, Daguerre, and Talbot, along with Sir John Herschel : who in 1819 discovered the suitability of hyposulfite of soda, or "hypo," as a fixing agent for sensitized paper images and who is generally credited with giving the new medium its name : deserve to share the title Inventor of Photography. Each made a vital and unique contribution to the invention of the photographic process. The process developed by Daguerre and Niepce was, in a grand gesture, purchased from them by the French government and given, free of patent restrictions, to the world. Talbot patented his own process and then published a description of it, entitled The Pencil of Nature (1844–46). This book, containing 24 original prints, was the first ever illustrated with photographs.
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