During the capturing of the film a beam-splitter in combination with filters in the camera divided the incoming light into a red and a green separation negative on black-and-white stock. When projected in the cinema the two images were combined simultaneously by additive mixture through corresponding red and green filters into one picture consisting of red and green colored light. The reduction of the whole color range to two colors (and their additive combinations) was necessary because of the complex optical arrangement.
The first subtractive 2 color process introduced by Technicolor captured the incoming light through a beam splitter with red and green filters also. However, in contrast to the first Technicolor process, the two b/w images were recorded on one negative strip. This was achieved by the pull-down of two frames simultaneously, a process that required the double speed in the camera. These two frames were arranged in pairs, whereby the green record was inverted up-side down (see image).
The third Technicolor process used the same camera as process no. II to combine a pair of frames of the red and green record respectively on the b/w negative (see image). In contrast to the former process, however, the two images were printed on one side of the positive by the dye transfer or imbibition process.