Editing 35 mm movie film (section)

===Modern 3D systems===
[[File:Over-Under 3D image.JPG|thumb|An "over-under" 3D frame. Both left and right eye images are contained within the normal height of a single 2D frame.]]
The success of digitally projected 3D movies in the first two decades of the 21st century led to a demand from some theater owners to be able to show these movies in 3D without incurring the high capital cost of installing digital projection equipment. To satisfy that demand, a number of systems had been proposed for 3D systems based on 35&nbsp;mm film by [[Technicolor]],<ref>{{cite web |url=http://www.technicolor.com/en/hi/cinema |title=Entertainment Services |work=Technicolor |access-date=29 August 2016 |archive-url=https://web.archive.org/web/20111024021545/http://www.technicolor.com/en/hi/cinema |archive-date=2011-10-24 |url-status=dead }}</ref> [[Panavision]]<ref>{{cite journal |title=Seeing is Believing |journal=Cinema Technology |volume=24 |number=1 |date=March 2011}}</ref> and others. These systems are improved versions of the [[3-D film#Revival (1960–1984) in single strip format|"over-under" stereo]] 3D prints first introduced in the 1960s.

To be attractive to exhibitors, these schemes offered [[3D film]]s that can be projected by a standard 35&nbsp;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 1970s. 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.

The Technicolor system uses the polarisation of light to separate the left and right eye images and for this they rent to exhibitors a combination splitter-polarizer-lens assembly which can be fitted to a lens turret in the same manner as an anamorphic lens. In contrast, the Panavision system uses a spectral comb filter system, but their combination splitter-filter-lens is physically similar to the Technicolor assembly and can be used in the same way. No other modifications are required to the projector for either system, though for the Technicolor system a silver screen is necessary, as it would be with polarised-light digital 3D. Thus a programme can readily include both 2D and 3D segments with only the lens needing to be changed between them.

In June 2012, Panavision 3D systems for both 35&nbsp;mm film and digital projection were withdrawn from the market by DVPO theatrical (who marketed these system on behalf of Panavision) citing "challenging global economic and 3D market conditions".<ref>{{cite web |url=http://www.dpvotheatrical.com/Home_Page.html |title=Home |website=DVPO Theatrical |url-status=usurped |archive-url=https://web.archive.org/web/20120407125922/http://www.dpvotheatrical.com/Home_Page.html |archive-date=2012-04-07 }}</ref>