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1727 Johann H. Schulze-silver salts turn dark when exposed to light.
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1780s Carl Scheele-changes in the color of the silver salts could be made permanent through the use of chemicals
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1830s Louis Daguerre, a French inventor, develops the first practical method of photography by placing a sheet of silver-coated copper treated with crystals of iodine inside a camera and exposing it to an image for 5 to 40 minutes. Vapors from heated mercury developed the image and sodium thiosulfate made the image permanent.
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1840s Josef M. Petzval, develops lenses for portrait and landscape photographs, which produce sharper images and admit lighter, thus reducing exposure time.
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1871 Richard L. Maddox-invents the "dry plate" process, using an emulsion of gelatin, so that photographers did not have to process the pictures immediately. By the late 1870s, exposure time had been reduced to 1/25th of a second. Gelatin emulsion made it possible to produce prints that were larger than the original negatives, allowing manufacturers to reduce the size of cameras.
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1885 American inventor George Eastman introduces film made on a paper base instead of glass, wound in a roll, eliminating the need for glass plates.
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1888 George Eastman introduces the lightweight, inexpensive Kodak camera, using film wound on rollers.
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1888 By developing films in its own processing plants, Eastman Kodak eliminates the need for amateur photographers to process their own