Autochrome
|
| Family group outdoors image by George Eastman House (Image rights) |
Autochrome plates are one of the first successful colour photography media, used in the early 20th century. The Lumière brothers' application for a patent was lodged in December 1903.[1] Plates were produced commercially by the Lumiere company from 1907 until 1934, by which time Lumière had produced Filmcolor, first sheet film and later roll film using essentially the same process.[2] Soon after this, however, a number of other successful colour media (Technicolor, Dufaycolor and Kodachrome) became available, which supplanted the Lumière products.
The Autochrome process is ingenious, using a single, monochrome silver emulsion to produce a true colour image. It had been known since the mid-19th century that a colour image could be produced by the addition of three component images, on three identical plates each exposed through a different coloured filter (and each also projected through a colour filter). Systems to make colour photographs by this method were sold,[3] but were not easy to use. The Autochrome plate offered a similar process in a single plate. It was not quite the first product to do so; a system was produced in Ireland by John Joly in the late 19th century, but was not commercially successful.[4]
The relative simplicity of the process, and the fact of its needing mostly facilities that photographers already had for monochrome plates, made colour photography possible for many amateurs for the first time.
On the front of an Autochrome plate is a three-colour filter layer. This is made from fine grains of starch, mixed from three batches dyed in different colours (orange-red, green and violet-blue), and applied to the glass plate in a layer one grain thick, stuck to the glass with lacquer, to form a random array of small colour filter elements[5] (the earlier Joly plates had the colour filters as thin stripes, spanning the whole plate[4]). Fine black powder (lamp-black, or soot) was also included in the filter layer, to fill any gaps between the grains and prevent the passage of unfiltered light. A coat of lacquer was applied over the filter layer, to protect it during handling and particularly during development.
The silver halide emulsion is therefore on the back of the plate; the exposure was made through the starch-grain filter and through the glass plate itelf. A sheet of black paper was normally placed behind the plate, to protect the emulsion from damage due to contact with the plate holder. Because the silver emulsion is more sensitive to the blue end of the spectrum, a special yellow filter was placed over the lens.
The plates were developed by a reversal process:[6]
- In the darkroom:
- First development to form a silver negative image
- Bleach stage to remove existing silver image in an acid solution of potassium permanganate, without affecting the remaining undeveloped silver halide
- The plates were then transferred to a daylit room (so remaining silver halide is exposed to light)
- Second development (development of the silver positive image made when the plates were exposed to daylight)
- Fix
- Wash
- Dry
- Varnish
The plates can be projected as lantern slides, or viewed against a light background (daylight or a lightbox). When Autochrome plates were produced, there was no straightforward way of duplicating the images.
The largest collection of Autochromes is that of the Albert Kahn Museum, including the work of Albert Kahn himself and many photographers working for him. Kahn's original project Archives de la Planète, comprises photographs and later film from many countries of the world. However, the work was interrupted by the First World War, which was also documented by many of Kahn's photographers. Some of the communities photographed for Archives de la Planète were radically changed by the War and subsequent history, so the Archives are a unique document of them.
Notes
- ↑ The Lumières' patent at Autochromes Lumière.
- ↑ Chronology of colour technology and products at Autochromes Lumière.
- ↑ for example, this three-colour separation negative and colour lantern slide produced from a similar plate, using a system sold by Sanger Shepherd & Co. in England, in the catalogue of the exhibition Cameras: the Technology of Photography at the Museum of the History of Science, Oxford.
- ↑ 4.0 4.1 Joly colour plate in the MHS exhibition.
- ↑ The making of Autochrome plates is described in more detail in Osterman, Mark (2003), The Autochrome Process at Notes on Photographs, a project of George Eastman House.
- ↑ Processing is described (in French) in this Autochrome Instruction Book: La Photographie des Couleurs et les Plaques Autochromes; Société A. Lumière et ses Fils, Lyon, c.1908 (displayed as a Flash object - not downloadable).
Links
- Autochromes Lumière, a project of the French Ministry of Culture.
- Albert Kahn Museum (site shows only a few of his Autochromes: this site advertising the BBC Book is better).
- Autochromes in the George Eastman House collection on Flickr
- Autochromes in the Bassetlaw Museum, Retford, UK in the Bassetlaw Museum's Flickr photostream.
- Autochromes of Villa Bonnier in the Swedish National Heritage Board's Flickr photostream.
- Autochromes Contemporains by Frédéric Mocellin (also his Flickr photostream).
