The first colour photograph showed red it should never have captured
In 1861 Thomas Sutton photographed a striped ribbon three times through coloured filters for a James Clerk Maxwell lecture, and the projected result showed red. A century later historians were baffled, because Sutton's plates were practically blind to red light. The answer turned out to be ultraviolet.
Maxwell had proposed the idea in an 1855 paper on colour vision. Using a spinning disc, he showed that any hue or grey could be matched by mixing just red, green and blue light in the right proportions, because the eye's three kinds of cone cells respond to those broad regions of the spectrum. Photograph a scene three times in monochrome through red, green and blue filters, project the slides back through the same filters, overlap them, and the full range of colour should reappear. Every practical colour process since, chemical or electronic, rests on that insight.
Maxwell himself complained during the lecture that the results were poor and that photography needed materials more responsive to red and green. The puzzle of the visible red was solved in 1961, when researchers found that many red dyes also reflect ultraviolet, which Sutton's red filter happened to let through. His three images were probably made by ultraviolet, blue-green and blue light, and the illusion worked anyway.
Before that, experimenters in the 1840s had hunted for a chameleon substance that would take on the colour of whatever light fell on it. Levi Hill's Hillotype of around 1850 managed mostly primaries, and Edmond Becquerel's images faded as soon as anyone looked at them in daylight. The real fix came in 1873, when the German chemist Hermann Wilhelm Vogel found that small amounts of certain dyes made emulsions sensitive to the colours those dyes absorbed. Becquerel added chlorophyll as a red sensitiser a year later, and exposures shrank from hours to minutes, then seconds.
The same three separations can build colour in two ways. Screens add red, green and blue light; prints subtract, using cyan, magenta and yellow dyes, with black added in printing. Colour has been photography's dominant form since the 1970s.
Source: Color photography
