A Dufaycolor colour transparency of the Cathedral in Ferrara, Italy, taken by an unknown photographer in about 1937. Built during the 12th century, it is one of the largest churches in the world. The Dufaycolor process was introduced as cine film in 1932 and as rollfilm for still photography in 1935. Based on Frenchman Louis Dufay's (1874-1936) Dioptichrome process of 1908, it was the last 'additive' colour process to be marketed and consisted of a very fine, regular filter screen made up of red, green and blue lines printed on a film base. Dufaycolor was popular with both amateur and professional photographers and survived until the 1950s.
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