trichrome process

The trichrome process in photography is a method for reproducing colors. Developed by Louis Ducos du Hauron in 1869, it involves taking three separate photographs of a scene, each through a different colored filter: green, orange, and violet. These negatives are then used to create three positives, typically as transparencies, using pigments of the complementary colors: red, blue, and yellow. When these three positives are superimposed, they create a full-color photograph. This process is a form of subtractive synthesis, where colors are achieved by removing certain proportions of light from white light.12