ENJOYED “FROM BLACK and White to Technicolor,” by Tom Huntington, in the Summer 2.001 issue. It mentioned James Clerk Maxwell’s extraordinary 1861 demonstration of photographic color reproduction, in which he photographed an object three times through red, green, and blue filters and projected positive transparencies together through the same filters. This experiment should have failed, since sensitizing dyes were not yet invented and thus his film could have been sensitive only to the blue light that silver halide could record. The red—and greenfiltered records should have been blank.
How did he do it? With the help of a series of coincidences. Strong blues and greens were separated because Maxwell’s green filter leaked slightly into the blue region, and since strong greens have some slight reflections in blue, the long exposures he gave the greens allowed that leakage to expose the film. For the red separation, it turns out that Maxwell’s red filter also transmitted ultraviolet, to which the film was sensitive, and synthetic dyes, such as that in the ribbon he was photographing, tend to have secondary reflectances in that spectral range. Maxwell became the father of modern color reproduction through serendipity.
Mitchell Rosen
SENIOR COLOR SCIENTIST
MUNSELL COLOR SCIENCE LABORATORY
ROCHESTER INSTITUTE OF TECHNOLOGY
ROCHESTER, N.Y.
