Autochrome of irises in silver vases, c 1910.

Autochromes were the first commercially available colour proces, invented by Auguste (1862-1954) and Louis Lumiere (1865-1948),, patented in 1904 and marketed in 1907. A glas plate was covered with potato starch, dyed green, red and blue, producing a random pattern of coloured dots and then coated with emulsion. This plate was then exposed in the camera with the glas side toward the lens, so that the starch acted as a colour filter on the light before it reached the emulsion. There followed a complex reversal development proces to produce a positive image on the plate which was then covered with another piece of glas to protect it.