Daguerreotype

The daguerreotype is an early type of photograph, developed by Louis Daguerre, in which the image is exposed directly onto a mirror-polished surface of silver bearing a coating of silver halide particles deposited by iodine vapor. In later developments bromine and chlorine vapors were also used, resulting in shorter exposure times. Unlike later photographic processes that supplanted it, the daguerreotype is a direct positive image-making process with no "negative" original.