Autochrome, the first widely used colour photography process, went on sale in France in 1907. Invented by the Lumière brothers, it recorded colour on glass through a mosaic of microscopic potato-starch grains dyed red-orange, green and blue-violet.
The brothers Auguste and Louis Lumière, already famous for their cinema projector, patented the process in 1903. Millions of starch grains, each dyed one of three colours, were spread across a glass plate, the gaps filled with soot, and the whole layer coated with light-sensitive emulsion. Each grain acted as a tiny colour filter. The plate was developed directly into a positive image on the glass, which glowed only when light shone through it or when it was projected. Exposures were far longer than black-and-white plates needed, so sitters had to keep still, and the random mosaic gave pictures a soft, dotted look reminiscent of pointillist painting. Autochrome remained the main colour process until the mid-1930s, when colour films such as Kodachrome replaced it.

