Ever since the invention by Alhazen (965-1040) of the pinhole camera, which projected an image onto a surface, people sought a way of "fixing," and thus recording, that image. By accident, in 1727, the German chemist Johann Schuize discovered that a mixture of chalk, nitric acid, and silver darkened when exposed to sunlight, and the rate of darkening increased if more silver was added. By 1777 the Swedish chemist Carl Scheele had been able to fix, or make permanent, the results of this change using ammonia.
Joseph Nicephore Niepce (1765-1833) produced the first permanent photographic image in 1826. He first used a flat pewter plate covered with bitumen, but then quickly moved on to silver compounds. Louis Daguerre produced silvered images that were very delicate and could not be copied. Although the exposure time was about ten minutes, he managed to produce daguerreotypes of famous people such as Abraham Lincoln (1846) and Edgar Alien Poe (1848).
Around this time William Henry Fox Talbot produced the calotype, in which an intermediate stage of the process resulted in a paper "negative" that could be used to make a multitude of final "positive" prints. Unfortunately, the paper and glass plates were wet. By 1884 George Eastman invented a dry process. Cameras became simple to use and all the complex chemistry could be left for later processing.
1907 heralded the commercial color photographic plate, and 1925 saw the introduction of 35-millimeter film. In the late 1980s, the manufacture of relatively inexpensive megapixel charge-coupled devices threatened the demise of film-based technology.
