Daguerreotype
The first commercially successful photographic process, producing a unique, highly detailed image on a polished silvered copper plate.
In depth
Announced in 1839, it exposed a plate sensitised with iodine vapour and developed it over heated mercury. The result is a mirror-like positive of extraordinary resolution that must be tilted to be seen properly, and it is unique — there is no negative and no way to copy it except by rephotographing.
Examples in practice
An 1840s daguerreotype portrait reveals fabric weave and individual hairs under magnification, from an exposure of several seconds.