A daguerreotype (original French: daguerréotype) is an early type of photograph, developed by Jacques Daguerre, in which the image is exposed directly onto a mirror-polished surface of silver bearing a coating ofsilver halide particles deposited by iodine vapor. In later developments bromine and chlorine vapors were also used, resulting in shorter exposure times. The daguerreotype is a negative image, but the mirrored surface of the metal plate reflects the image and makes it appear positive when the silvered surface has a dark ground reflected into it. Thus, daguerreotype is a direct photographic process without the capacity for duplication.
The daguerreotype was the first publicly announced photographic process and while there were competing processes at the time, the accepted scientific etiquette of the time was that discovery was attributed to first published. All of the initial photographic processes required long periods for successful exposure and proved difficult for portraiture. The daguerreotype did become the first commercially viable photographic process in that it was the first to permanently record and fix an image with exposure time compatible with portrait photography, but this was after extra sensitising agents (bromine and chlorine) were added to Daguerre's original process.