Ravenstein around 1920

by Raoul Suermondt

Scan of a relatively rare autochrome plate from the photo archive of the Suermondt family. On the glass slide you can see a cityscape of the North Brabant town of Ravenstein around 1920.

Autochrome was invented by the French brothers Auguste and Louis Lumière. In 1907 they started with the production of autochrome plates. An autochrome is a color slide on glass. Between two glass slides a color screen was applied to a light-sensitive layer of black-and-white emulsion. This grid consisted of millions of minuscule potato starch grains that were painted in the colors orange, violet and green. The starch granules let the light of their own color through and absorb their complementary colors. The emulsion was thus always locally exposed through only a part of the spectrum. Autochrome is an additive color process, based on the principle that the three primary colors (red, green and blue) produce all other colors by mixing. For example, red and green produce yellow. The starch granules in this autochrome photo provide a nice pointillistic effect.

For making an autochrome recording, in principle every camera was eligible. Autochrome plates were supplied in many sizes: from 4.5 × 6 to 18 × 24 cm. The lighting was critical. Because of the thin emulsion, she easily overexposed or underexposed. Hard sunlight had to be avoided as much as possible. Due to the low light sensitivity, long shutter times were required. So fast snapshots could not be made.