The three-strip Technicolor process used three strips of black-and-white film (hence the "three-strip" designation) and a beam splitter or split-cube prism. The prism split the light into three components: green, red, and blue. The green component was registered onto a strip of panchromatic black-and-white film; the blue was registered onto a strip of red-emulsion-coated black-and-white film; and the red was registered onto another strip of red-senstive panchromatic black-and-white. The red and blue strips were mated back-to-back, in a "bipack" arrangement, with the blue-sensitive film in front.
To print the film, each colored strip had a "relief-positive" print struck from it, which was then bleached to remove the silver and then soaked with a dye that was the exact chromatic opposite of the color in question: cyan for red, magenta for green, and yellow for blue.
Each of the three dye-soaked strips were brought into contact with a single clear strip of film, with each color built up in a successive pass. Such a process was referred to by Technicolor as "dye imbibation", which was commonly used in conventional offset printing or lithography but which the Technicolor process adapted to film. The final strip of film would have the dyes soaked into it and not simply printed onto its surface, which produced rich and deeply saturated color.
Sometimes the clear film would be pre-exposed with a composite panchromatic black-and-white positive image derived from the other three negatives, as a way to deepen the blacks and heighten the contrast of the image.
Technicolor originally existed in a two-strip (red and blue/green) system, and then as a subtractive color system where the color information was carried directly onto the film and not projected through filters. Toll of the Sea debuted on November 26, 1922 as the first general release film to use two-tone Technicolor (The Gulf Between was the first film to do so but it was not widely distributed). A four-strip technicolor process was also used on a few films in the 1940's. The fourth strip was simply black-and-white and improved contrast.
One major drawback of Technicolor's 3-strip process was that it required a special Technicolor camera. Also, the process of splitting the image through a prism reduced the amount of light that reached the film stock. Since film speeds were fairly slow in the 1930s-1940s to begin with, early Technicolor productions required an excessive amount of lighting.
When Eastman Kodak released its one-strip color negative film it meant Technicolor prints could be struck from a single camera negative exposed in a standard camera. However, in the mid-1950s Kodak also introduced a means of producing prints through standard photographic processes (as opposed to the expensive dye imbibation process). This meant studios could make color prints in their own labs, rather than having to send them to Technicolor.
Technicolor eventually fell out of favor in the United States as being too expensive. The last major American film released in Technicolor was The Godfather, Part II (1974) In 1975, the last three-strip plant was closed and sold to Beijing Film and Video Lab in China; a great many films from China and Hong Kong have since been made in the Technicolor process.
The Technicolor company remained a higly successful film processing firm and later became involved in video and audio duplication (CD, VHS and DVD manufacturing) and digital video processes.
By the late 1990s the dye-transfer process still had its advantages. Its distinctive "Technicolor look" was hard to obtain by any other means, and it remained the most archivally stable color process. In 1997 Technicolor reintroduced the dye-ibibation process to film production.
An article on the 1997 restoration of Star Wars Episode IV: A New Hope (original version 1977) claimed that a rare dye-transfer print of the movie, made for director George Lucas, had been used as a color reference for the restoration.
The company was purchased by Thomson Multimedia in 2001.