Wonderful Autochrome effect for the retro 20’s look. Autochrome had been a color positive transparency process created by Lumiere in 1907 and as used by such photography greats as Edward steichen and alfred stieglitz, just among other things. The method consisted in coating a glass plate using a random mosaic of microscopic grains of potato starch dyed red, green and blue which work as color filters. These rather coarse grains of starch gave a hazy, pointillist effect for the overall image.Inside the digital age we will recreate this effect while using digital noise.
The first thing we’re going to do is to try to recreate the Autochrome color caracteristics. One thing to bear in mind is that since this was an early color process, color rendition was not always faithful and consitant. Another thing is, from the autochromes I have seen, color deterioration is a big issue. Usually there are alot of color streaks and stains. Sometimes a green color cast developes on certain parts of the image making it difficult to imagine what the original subtle colors might have been. Having said that, no two autochromes are alike. So when working on your image perhaps it would be a good idea to search for examples on the web to get an idea of what kind of colors where achievable. There are however, certain general caracteristics. Usually autochromes were quite dark and low in contrast. This was mainly due to the fact that they needed a long exposure for a proper image and that besides the potato starch dyes, they also had a layer of panchromatic silver hylides emulsion(the stuff found in regular B&W film).
Visit your curves adjustment by simply clicking the “new layer adjustment” icon in the bottom within your Layers Palette. Layers Adjustment
You start with the red channel, what we need to do will be to drop the curvature a little. Do that by making a new point there in curve and setting the Output to 120 plus the Input to 130. You may make the bend dip a bit deeper according to the image but you need to avoid a green color cast.
With all the green channel you need to create the same curve only these times, be sure to stop before getting a magenta cast.
With all the blue channel we need to get it a little further. In such a case I gave it an Production of 150. Usually Autochromes were more from the warm side with the color scheme.
What this curve adjustment will work is offer you image a warm pastel look but you want it even warmer so open your Photo Filter adjustment layer.
The Photo Filter will act just like you have got your photograph with the actual color filter in your lens. Autochromes used a different special orange-yellow filter from the camera mainly to prevent ultraviolet light and restrain the impact of violet and blue light which are areas of the spectrum in which the emulsion was extra sensestive. In this instance, we’re visiting select a Warming Filter (85) and place it’s Density to 50%. This value could vary according to your image.