Autochrome

Autochrome is the first colour process anybody could buy and use, and it looks like nothing that came after it. The colour is not a dye layer and not a filter. It is a screen of millions of dyed starch grains, so every area of the picture is a mixture of small orange red, green and blue violet points. The eye adds them together, and the result is a mosaic rather than a smooth wash.

The second thing to know is that it is quiet. The screen absorbs most of the light, so nothing reaches full saturation and the whole picture sits in a pastel range with a slight grey cast. That muted colour is the character of the process. A vivid autochrome is a contradiction, and a prompt that asks for rich colour destroys the look.

Describe the screen. A glass plate carries a single layer of potato starch grains, dyed orange red, green and blue violet, each grain about four to six microns across, roughly four million to the square inch. Lampblack fills the gaps between them, and a varnish seals the layer. A panchromatic emulsion goes on top, and the plate is exposed through the glass so the light passes the screen first.

Set the colour behaviour. Warm tones come through strongly, greens are reasonable, and blues are weak and often go grey. Skin reads pink and slightly chalky. Ask for low saturation, a pastel range and a slightly muddy cast, and ask for the grain structure to be visible rather than smooth.

Set the exposure and the object. The plate is roughly sixty times slower than the black and white plates of its day, so every picture needs a tripod and an exposure of seconds. Say that a sitter is braced and still, and that leaves and water blur. The finished plate is a transparency on glass, viewed by transmitted light in a viewer or projected, so ask for the glass, the mount and the varnish crazing at the edge.

Use it for a garden, a flower study, a costume, a still life or a seated portrait in daylight. Those are what people actually photographed on autochrome plates, because they hold still and because warm colours record best.

Leave it alone for anything fast, dim or blue. Night, water sports and a clear sky all fail: the exposure is too long, and the blue end of the palette comes back weak and grey.

Kodachrome 64 is the colour transparency most people picture from the twentieth century. It arrived in 1935, thirty years later, with dye couplers, real saturation and a film base. Autochrome has no dyes in the image at all, only a screen of coloured grains in front of it.

Cinema publishes Vintage at /techniques/cinema/, a grade where colour behaves like film stock that aged on the shelf. Autochrome is not aged film. It is a screen plate that was pastel on the day it was made, and its grain is a mosaic of round starch grains rather than a film texture.

Velvia 50 and Ektachrome E100 are the modern transparency references, and both are clean and saturated. Naming one of them beside autochrome pulls the picture straight back to a modern slide.

The Lumiere brothers patented the screen plate in 1903 and sold plates from 1907, and it stayed the practical colour process for the next twenty five years. National Geographic printed its first autochrome in July 1914, a flower garden in Ghent, and ran hundreds more through the 1920s, which is why the magazine is where most people have seen the look. Photographers used it for gardens, costume, still life and portraits, always on a tripod. Lumiere moved the same screen onto a film base as Filmcolor in 1932, and the glass plates stopped. Surviving plates are fragile, and many carry cracks or crazed varnish at the edges.

The model returns a saturated modern colour photograph with a warm grade. Say the colour comes from a mosaic of dyed starch grains, the saturation is low, the range is pastel and the cast is slightly muddy.

The second failure is clean fine grain like a modern film. Say the grain is a visible pointillist mosaic of round dyed grains, in orange red, green and blue violet.