Louis Daguerre invented the daguerreotype, a photographic process which produced a single positive image, in 1839. He used iodine on a silver-coated copper plate to obtain a coating of silver iodide on the plate. When he exposed it to light for several minutes, the plate turned dark where light fell on it. The resultant plate produced an exact, though laterally reversed, image of the scene.
Daguerreotypes were usually portraits, taking several minutes to expose and requiring the subject to remain stock still. Daguerrotypes of streets of Paris did not show any humans because the long exposure times required to expose the image meant that all moving people were not still long enough to be recorded.
Millions of Daguerreotypes were produced, but by 1851, the year of Daguerre’s death, the Fox Talbot negative process was refined by the development of the wet collodion process, whereby a glass negative enabled a limitless number of sharp prints to be made. These developments made the Daguerreotype redundant and the process very soon disappeared.