File:Jan Szczepanik - one of firsts colour photo.jpg

English: A photographic colour print made on a bleach-out type of printing paper developed by Jan Szczepanik and marketed by Agfa around 1910, which made use of the fact that a dye of a particular colour is most strongly bleached by light of the complementary colour. Superimposed dye layers of the subtractive primary colours cyan, magenta and yellow are therefore eventually bleached to the colour of the light falling on them. The basic principle was the subject of experiments by Sir John Herschel in the 1840s; its application to three-colour photography was conceived and published in an essentially complete form by Louis Ducos du Hauron later in the 19th century. In practice, long exposures in direct sunlight were necessary and the results could not be made sufficiently light-fast to allow prolonged open display without fading. Little-used, such papers were most suited to printing under painted or stained glass or art glass, but they were primarily marketed to photographers who wanted to make paper prints from Autochromes and other early glass-based colour photographs.