Autochrome History

Originally published: April 9, 2011

The Autochrome process was the first color photographic process. It was created by the Lumiere brothers who were well known for their filmography. The plate utilized died starch grains (Red, Green, Blue) to create a color filter infront of a black and white (silver nitrate) emulsion. This process is very similar to the way that a modern digital camera interprets colors. There are filters (starch grains in Autochrome) positioned in front of the digital sensor (silver nitrate film emulsion) that allow different wavelengths of light (different colors) to pass and create the end image with multiple colors and varying tones. The autochrome process produces a particular aesthetic because of the way that it is created and consequently is of interest.

This is what I have been able to piece together through varying online and physical books and essay of the original makeup of an autochrome plate. Since the technology has long since been extinct it has been difficult to discover the truth about production and physical and chemical make up of the plate. This also creates great difficulty in reference to finding an expert who can aid me in my attempts to improve and modify the process.

An autochrome plate was used in a large format camera to create a picture. The plate itself was glass. The next layer would be the black and white emulsion, typical to any large format glass plate. The black and white emulsion was typically made of silver nitrate or some similar photosensitive compound. The next layer was a non-water soluble layer (required for development) that encased the black and white emulsion layer. From what I have been able to gather this was done via some sort of varnish, it is believed that this was accomplished with dammar resin. Then a layer of some adhesive material was added to prepare the plate for the addition of the colored starch grain color filter. The color filter was made up of deep red, green and blue died starch grains (more so then in the graphic which is for illustrative xpurposes only.) Then a final layer of varnish or other material was used to encapsulate the entire plate, which again was required for the development process. The whole plate was the placed in the camera with the starch grain filter being the first area that light would pass through. The varnishes were as clear as possible so that they would not significantly affect the image. However if you look at an autochrome plate it has the photographic attribute of being “warm” that is to say having more brown and orange overtones, which could have been an impact of the traditional color of varnish.

Layer A is the glass plate. This was simply a piece of clear glass that provides the rigid backbone that they entire structure of the autochrome plate is attached to. Typically the glass plate was in the 4×5 inch category however theoretically it is possible to use the autochrome plate with any sized piece of glass and a large format camera assuming that you can fabricate the required holder for the glass plate.

Layer D is the black and white silver nitrate emulsion. This emulsion is a light sensitive compound like you would find in any other black and white glass plate or piece of film. One of the problems that this original method encountered was that it was, in photographic terms, a slow emulsion. This means that it does not have a high sensitivity to light. In photography light sensitivity is denoted in ISO (previously ASA), which is a numerical value that denotes the sensitivity to light of an emulsion or film. The general standard used in both digital and analog cameras as ISO 400, which has a resolving, power capable of fast shutter speeds and clear (non motion blurred) Images. The resolving power of the emulsion used in an autochrome plate was roughly ISO 1 or ISO .5 which is to say extremely slow. Consequently it was as it was with other photographic processes at the time difficult to take photos because of movement of the subject as well as the camera while the film or glass plate was being exposed to the light.

Layer E is the first layer of varnish that was used. This layer was utilized to encapsulate the silver nitrate photographic emulsion layer. This is required for the development process of the autochrome plate.

Layer F was some form of non-water soluble adhesive that allowed the starch grains to remain on the plate. It is necessary that the adhesive and encapsulating layers be polar because water is one of the items used in the development process of this plate.

Layer B is the most important layer of the autochrome process. This is the layer that is formed by the different colored starch grains as well as the lampblack (commonly known as charcoal to fill the spaces.) The colors used to die the starch grains were Rose Bengal, Malachite Green, Tarrazine, Crystal Violet,  Erythrosin B (Acid Red 51), and Methylene blue. All of these dies used are characterized as triphenlmethane dies because of their chemical structure. They are deep colors that translate into the different tones when the photograph is exposed. Because of their high density and small particle size approximately 10-15 microns.

Layer C is simply another layer of the varnish. This final layer is used to encapsulate the entire plate and make it water resistant for the development process.

3 Responses to Autochrome History

  • Hi Brian,

    Great post – very informative. We’re very interested in autochromes, and in fact are lucky to have some very rare early autochromes taken by the Lumiere Brothers themselves during 1907-11. You can see them on our (now quite outdated) website and we still have some of the images for sale (they are collector’s items). We will be relaunching our website in quite a major way in January, and it will also contain much more information.

    Meantime, you may like to know that the French government-funded research institute CNRS has done a lot of research on autochromes, including remaking them. You can do a Google translate of this page:

    http://www2.cnrs.fr/presse/journal/4524.htm

    The last link includes a video of Bernard Lavedrine making an autochrome plate.

    Also, this guy in France has made some recently: http://www.autochromes.fr/

    More generally, you may have seen this great site by the French Ministry of Culture: http://www.autochromes.culture.fr

    Hope this helps,

    Aebhric

    • admin says:

      Thank you, those have some great information, and I had not previously known about them. I’m reading through them now, I will be posting some high-resolution scanner and microscope-camera images of the plates I have soon, in another report on my research.

  • Steve says:

    Did you ever publish your report on your research? If possible, I would like to see it.

    Thanks.

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