Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!dogie.macc.wisc.edu!decwrl!henry.jpl.nasa.gov!elroy.jpl.nasa.gov!cit-vax!mickey!jim
From: jim@mickey.UUCP (jim houston)
Newsgroups: comp.graphics
Subject: Re: polarized film?
Keywords: 3-D, film, stereo-viewing
Message-ID: <112@mickey.UUCP>
Date: 16 Oct 89 05:48:15 GMT
References: <475@alias.UUCP>
Organization: Walt Disney Pictures, Glendale, CA
Lines: 31

In article <475@alias.UUCP>, pearce@alias.UUCP (Andrew Pearce) writes:
> 
> My question is, what are the actual mechanics of placing the two images on
> film? Is the film double exposed, once for each image of the stereo pair,
> with different polarization each exposure? Does the film grain retain this
> polarization? Or is it a special type of film with a polarized emultion on
> each side?
> 

The separation is achieved in the projection of the film, not in the recording
of the image. In the simplest method, two cameras are used to create two strips
of film; one for the left eye and one for the right. Each strip is developed
normally and a print is made. The prints are projected onto an aluminized 
screen using a pair of inter-locked projectors containing different 
polarizing filters 

Other methods have been used however. The trick is placing the stereo pair 
on the film in a layout that matches the projection system that will be used.
As an example, over-under pairs can be used. In this format, both "eyes"
are recorded on the same strip of film. One frame of 35mm film will contain
the right eye in the top half of the frame and the left eye in the bottom half.
A special lens is then used on the projector to overlay the images on the screen.
Other formats can be used as well. The images can be placed on the film
as two squeezed (i.e. anamorphic) images on the left and right half - again
requiring a special lens to properly split and project the image.

I don't know exactly which format was used at SIGGRAPH for the 3D films.


Jim Houston
Walt Disney Pictures