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Sir John Herschel first used the word photography, which is derived from the Greek words for light and writing, in 1839, the year the photographic process became public. There had been previous attempts to make photographs using two different methods, but they had never been successfully combined.
The first method was optical. Since the 16th century artists and scientists had made use of the fact that light passing through a small hole in one wall of a dark room, or camera obscura, projects an inverted image on the opposite wall. The hole was soon replaced with a lens, which made the image brighter and sharper. By the 18th century a port...