The Collodion or Wet Plate Process
Collodion process, mostly synonymous with the "collodion wet plate process", requires the photographic material to be coated, sensitized, exposed and developed within the span of about fifteen minutes, necessitating a portable darkroom for use in the field. Collodion is normally used in its wet form, but can also be used in humid ("preserved") or dry form, at the cost of greatly increased exposure time. The latter made it unsuitable for the usual portraiture work of most professional photographers of the 19th century. Its use was therefore mostly confined to landscape photography and other special applications where minutes-long exposure times were tolerable.