Autochrome Lumière
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The Autochrome Lumière is an early color photography process. Patented in 1903 by the Lumière brothers in France, and marketed in 1907 it remained the principal color photography process available on the market until 1935.
Autochrome is an additive color 'screen-plate' process: the media contains a glass plate, overlaying random mosaic of microscopic grains of potato starch, with lampblack filling the space between grains, and a black and white silver halide emulsion. The grains are a mixture of those dyed orange, green and blue, and act as color filters. The plate is processed as a slide, (that is the plate is first developed to a negative image and then reversed to a positive image) and the starch grains remain in alignment with the emulsion after processing in order to allow the colors to be seen properly.
To create the original Autochrome plates, a slightly concave glass plate was coated with a mixture of pitch (crude pine sap), and beeswax. The starch grains, which had been sorted by size and dyed, were sprayed on top of the plate. It was later discovered that applying extreme pressure to the plate would improve the quality of the image, as the starch grains would be flattened slightly. Lampblack was then applied by a machine, in order to fill the clear spaces between the grains. After this, the plate was coated with shellac. This served to protect the color mosaic, and to provide a flat surface for the emulsion, which was spread on the plate once the shellac dried.
The patent application describes the process somewhat differently: the grains are Red, Yellow and Blue (no blacklamp filling) and there are two layers of them, therefore when grains of different colors superimpose, this creates Orange, Violet and Green zones as well. The total surface is therefore covered with 6 different tints. It is still necessary to invert the image to obtain a positive.
Small autochromes could be viewed using a hand-held transparency viewer, but large ones required a special device. Called a "Diascope" this was a flat case holding the autochrome image and a ground glass diffuser in one side and a mirror in the other. A user would let light pass through the autochrome and view the image in the mirror. If the Autochrome is well made the color values are very good. Unfortunately the dyed starch grains are somewhat coarse giving a somewhat hazy effect with stray colors often appearing, expecially in open light areas like skies.
Autochromes were glass plates until the 1930s when a film format appeared as well.
Autochrome film was gradually replaced by other processes, including Kodachrome, Agfacolor Neue and Kodacolor.
In February 2006 an 1904 autochrome - "The Pond-Moonlight" by Edward Steichen - was sold in auction at Sotheby's in New York by the Metropolitan Museum of Art. The anonymous buyer paid $2.9m, a record for a photographic print. [link]
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