Autochromes are color transparencies on glass plates that are viewed either in special viewers called diascopes or projected onto a screen. They were also commonly placed on window panes using a brass frame with two suspension hooks.
The first practical color process, the Autochrome was one of the few commercially successful additive color processes, available since 1907.
Autochromes were made by coating a glass plate with a mosaic of minute potato starch grains dyed to approximate the primary additive colors of light. This was then coated with a panchromatic silver emulsion. Exposed in a camera so that the color mosaic filtered the light before it reached the emulsion layer, the plate was processed to create a black-and-white positive. This, in combination with the color mosaic, created a photographic image in natural colors.
Autochrome plates were manufactured from 1907 to the 1930s by the Lumiere brothers, who also figure prominently in the early history of motion pictures.