Lexicon
Daguerreotype

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The daguerreotype (French: daguerréotype) was the first commercially successful photographic process. The image is a direct positive made in the camera on a silvered copper plate. The raw material for plates was called Sheffield plate, plating by fusion or cold-rolled cladding and was a standard hardware item produced by heating and rolling silver foil in contact with a copper support. The surface of a daguerreotype is like a mirror, with the image made directly on the silvered surface; it is very fragile and can be rubbed off with a finger, and the finished plate has to be angled so as to reflect some dark surface in order to view the image properly. Depending on the angle viewed, and the color of the surface reflected into it, the image can change from a positive to a negative.

(Wikipedia)