Autochrome is an early colour photographic process created by the Lumiere brothers in France in 1903. It was the main colour photographic process available to photographers until as late as the 1930s when Dufaycolour became popular. It consists of a glass plate coated on one side with microscopic grains of strach dyed red-orange, green and blue-violet, the grains act as colour filters. Lampback fills the spaces between grains and a black ans white panchromaticsilver halideemulsiom is coated on the top of the filter layer. The autochrome was loaded into the camera with the bare glass side facing the lens so that the light passed through the colour filters before reaching the photographic emulsion. The plate is processed to produce a positive transparency. Light, passing through the coloured starch grains, combines to recreate a full colour image of the original subject.

Unlike ordinary black-and-white plates, the Autochrome was loaded into the camera with the bare glass side facing the lens so that the light passed through the mosaic filter layer before reaching the emulsion. The use of an additional special orange-yellow filter in the camera was required to block ultraviolet light and restrain the effects of violet and blue light, parts of the spectrum to which the emulsion was overly sensitive. Because of the light loss due to all the filtering, Autochrome plates required much longer exposures than black-and-white plates and films, which meant that a tripod or other stand had to be used and that it was not practical to photograph moving subjects. The plate was reversal-processed into a positive transparency that is, the plate was first developed into a negative image but not “fixed”, then the silver forming the negative image was chemically removed, then the remaining silver halide was exposed to light and developed, producing a positive image.