The Autochrome Lumiére was introduced in 1907 and was the primary process used to make color photographs until the introduction of color film in the 1930s. A glass plate was coated with a random mosaic of grains of potato starch died red, green, and violet. Lampblack filled the spaces between the grains. A panchromatic silver halide emulsion is added. After exposing in the camera the plate is developed then reversed as a positive. The starch grains act first as filters for the colors striking the plate and then as a viewing filters in the finished image. For example light from a green leaf will pass through the green particle and expose the emulsion under it but would not pass through the red or violet particles. On viewing by transmitted light the green color would show wherever green light hit the plate.
