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AutochromesThe Autochrome plate of the Lumière Brothers is a direct positive, on a glass plate, of variable size; there is no negative so they are unique non reproducible (in a direct manner) photographs, precursors of color slides:
Louis Lumière had already invented instant photographic plates and the Cinematograph when, in late 1903, he and his brother Auguste patented a new process for producing color photographs: the Autochrome.
Exposure (which may vary from several seconds to several minutes according to the intensity of the light, the luminosity of the subject and when it was made) is taken with the filter side of the plate turned towards the lens. A yellow-orange filter is placed on the front of the camera lens; its role is to compensate for the excess activity of violets and blue radiations.
"Before the invention of the Autochrome, colors were separated using a complex three-color process whereby three successive exposures had to be taken and then superimposed onto each other. Louis Lumière, however, devised a method of filtering light by using a single three-color screen made up of millions of grains of potato starch dyed in three different colors. This mixture was then laid out on a varnished glass plate, which would be ready for use once it was coated in a black and white emulsion. Developing the plate entailed applying the same process as was used for black and white photographs at the time, with the impression being processed to reversal.
As with pointillist painting, the color effect is rendered by viewing the image in its entirety, since the colors are created from the juxtaposition of the multitude of dots; indeed, the essential charm of these photographs derives from that very juxtaposition.
Finally, in 1907, after years of work, the Autochrome was launched onto the market and met with immediate and long-lasting success - it was to be another thirty years before anything else came along to compete with it, and that was when chemical color processes were devised to do on film what this delicate transparency process did on glass."
(Definition of the Autochrome by the Lumière Institute in Lyon-France)
The Autochrome plates were intended to be projected with a lantern lit by an arc lamp which gave a powerful light and allowed considerable enlarging on giant screens; or they could be individually admired using a clever system: the diascope, a leather or fabric case provided with a frame and a mirror. The frame maintains the Autochrome plate on a tilted level. When this one is placed under a source of light, it is reflected on the mirror inside the case. For an optimal vision, the mirror is protected from the ambient light by two side bellows. In order to protect the fragile emulsion of the Autochrome plate, a protective glass was placed on top of the original glass plate, secured by a special "binding tape" that ensured the sealing of emulsion and its protection from the moisture and the air pollution.
Eventually, the grain pattern of the Autochrome was applied to films (cellulose nitrate) which allowed for greater sensitivity allowing instantaneous color photography. The first method of sheet film produced by Lumière was called Filmcolor in 1932. In 1934 a color roll film called Lumicolor was also availaible.
The Autochrome was destined to be abandoned in 1935-36 when Kodak laboratories developed Kodachrome soon to be followed by the paper processes of Kodacolor (1942). The German Agfa-color was introduced in 1943, which definitively put small size color photography within everybody‘s range. The Polacolor of E.H. Land, an instantaneously developed process appears in 1952 and it evolved into the household name Polaroid in 1972.
Nadia Valla (2006)