Duplitized film
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Duplitized film stock was a type of film available through various companies used in color photography and special effects. It was introduced in the early 1910s. The stock was of standard gauge and thickness, but carried an emulsion on each side of the base. For a color process such as Cinecolor or Prizma, red and blue or red and green negatives would be exposed, one to each emulsion. From there, its appropriate colors were converted from black and white to color by means of toning both emulsions their appropriate color.