Autochrome

  • Autochrome

  • Autochrome

    The autochrome plate was the first three-color photography process on the market and belongs to the group of additive color processes. The medium consists of a mosaic of colors on a glass plate, designed to be viewed using hand-held devices or projected using carbon arc lamps.

    The plates were patented in 1904 by the Lumière brothers, produced and marketed starting in 1907 by the Lumière company, and a popular success until Kodachrome was released in the early 1930s. Production stopped in 1932, although the process was still used on flexible film sheets until 1955.

    In this process, a glass plate coated with a latex-based varnish is covered with a thin, regular layer of grains of potato starch dyed green, blue, and red-orange.
  • Autochrome

    To produce the negative part of this unique object, one side of a clean glass plate is covered with a thin layer of collodion containing ammonium or potassium halides (iodide or iodide and bromide). This collodion emulsion is richer in ether than the one used for producing conventional collodion negatives so as to produce a whitish image, making it show up better against the dark background used for viewing it. Dipping in a silver nitrate solution ensures that it will be uniformly sensitive to light prior to exposing the plate when still wet. After development in a nitric acid and iron sulphate developer, sometimes with added silver nitrate, the image is fixed in a bath of sodium thiosulphate or potassium cyanide. Using iron sulphate gives the ambrotype its characteristic creamy tint. After drying, a transparent varnish is applied, and sometimes, additional colour highlights.

    The dark background against which the negative is placed may be of various kinds: paper, velvet or a varnish made from a base of bitumen of Judea and turpentine. It is then laminated by a roller press developed by the Lumière brothers. Afterward, the color mosaic is coated with a layer of resin-based shellac over which is layered a light-sensitive silver-gelatin emulsion, which may be varnished as well.
  • Autochrome

    The plate can then be exposed from the back in the camera and then developed and reversal-processed into a positive transparency.

    A process similar to autochrome was developed in the 2000s by Frédéric Mocellin, who produces color mosaic transparencies by hand on a polyester medium.

    Visual glossary of photographic techniques © ARCP / Mairie de Paris, 2013

    Images from the top:
    Anonyme, Jeune femme en costume traditionnel sous un arbre en fleurs- Jardin méditerranéen, Plaque autochrome © Cinémathèque Robert Lynen / ARCP / Mairie de Paris / cl. Jean-Philippe Boiteux
    Enlarged detail x3 © Reproduction : ARCP / Mairie de Paris / Jean-Philippe Boiteux.
    Enlarged detail x 30 © Reproduction : ARCP / Mairie de Paris / Jean-Philippe Boiteux.


Glossary

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