Page "VistaVision" Paragraph 8

Paramount took this concept a step further, using old Stein cameras that were originally meant for an aborted early 1930s color process.

For the color process, instead of an image four perforations high, the camera exposed eight perforations ( essentially two frames ) consisting of one 4-perf image through a red filter and one 4-perf image through a green filter.

In shooting VistaVision, the film was run horizontally rather than vertically, and instead of exposing one 4-perf frame twice, the entire eight perforations were used for one image.