A darkroom effect in which an image is partly positive and partly negative. It happens when a print or negative is briefly exposed to light during development, then developed further. Thin light lines, called Mackie lines, often appear along the edges between light and dark areas. The French scientist Armand Sabattier described it in 1862.
Man Ray (1890-1976) made it famous. Around 1929 his assistant Lee Miller (1907-1977) accidentally turned on a light in the darkroom. Man Ray liked the result and used it on purpose in many works. He called it "solarization", but true solarization is a different effect caused by extreme overexposure. Today the look can also be imitated in editing software.
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