Page "35 mm film" Paragraph 20

To be attractive to exhibitors, these schemes need to offer 3D films that can be projected by a standard 35 mm cinema projector with minimal modification, and so they are based on the use of " over-under " film prints.

In these prints a left-right pair of 2. 39: 1 non-anamorphic images are substituted for the one 2. 39: 1 anamorphic image of a 2D " scope " print.

The frame dimensions are based on those of the Techniscope 2-perf camera format used in the 1960s and ' 70s.

However when used for 3D the left and right frames are pulled down together, thus the standard 4-perf pulldown is retained, minimising the need for modifications to the projector or to long-play systems.

The linear speed of film through the projector and sound playback both remain exactly the same as in normal 2D operation.