In 1972 or 73 (and I admit it’s so long ago that I can’t remember which year it was) I began to devote myself to stereoscopic filmmaking and technology. That led eventually to the publication of my book Foundations of the Stereoscopic Cinema, and it also led to my career as an inventor in the field.

The first experiments I did involved using super-8 cameras and projectors – specifically Beaulieu and Nizo cameras, and Eumig projectors. The Eumig projectors could be interlocked using a timing belt with a declutching mechanism, and I could really achieve good precision with regard to shutter phase, which allowed me to reproduce some of the experiments that had been described in the literature, specifically by Jones and Shurcliff in the SMPTE Journal of the early fifties. The cameras were interlocked using hardware that I got from Super8 Sound with devices originally made for synchronizing a super-8 camera with a magnetic recorder.

I did a lot of work trying to figure out the basic parameters for doing good stereoscopic photography, and I actually had a fairly flexible system. I projected on a Kodak Ektalite screen that did a wonderful job of conserving polarization and had very high gain. For quite a few years I did experiments in my laboratory in Point Richmond, California.

I wanted to do stereoscopic zooms and in 1973, or maybe 74, I tried it and I learned a lesson that other people have learned: they’re difficult to do. At the time I thought I may have been one of the first people to try successfully to pull it off. I was informed on the subject by an article that was written by a Kodak researcher, MacAdam, which one can also find in the SMPTE Journal. Stereoscopic zooms, it was alleged by some, were assumed to be a no-no – something you can’t do, something that won’t work. The idea was that the effect would be perceptually disturbing. As I look back on it now, I wonder why people say no to something, not having seen it.

As a matter of fact, stereoscopic zooms work well perceptually but there are all kinds of technical “gotchas”. One of the most important gotchas has to do with something that I defined as the centration vector, and I filed a patent for the cure for the stereoscopic zoom problem in U.S. Patent No. 4,418,993, filed on May 7, 1981. This was my first patent filed years after I did the work. At the time I had no idea I’d be starting a business and when I did I filed the patent.

There are a couple of problems with stereoscopic zooms, and these are mechanical/optical problems, and have to do with the fact that as you zoom the lenses the optical centers wander and the left and right images shift side to side or up and down depending upon on the location of the new optical center. When you have two zoom lenses there’s no guarantee – in fact, it’s improbable – that the lenses’ centers are going to shift in the same direction and in the same way. This means that you are going to create spurious or unwanted parallax in the vertical and/or the horizontal direction. One leads to difficult fusion and the other to more or less parallax than you bargained for changing the location of the zero parallax plane – or that which is meant to appear in the plane of the screen.

Another problem has to do with linking the two zooms so the focal lengths are exactly the same frame-for-frame, or field-for-field. And there are other problems such as those related to focus. You’ve got to focus the two lenses in a coordinated fashion, and focusing can change magnification too. I mentioned my early efforts to Peter Anderson, and he is possibly the most experienced stereoscopic cinematographer in the world having shot many theme park and IMAX shows. Peter and I are co-chairs of the ASC Technology Committee Stereoscopic Cinema Subcommittee. I’m going to let Peter talk for himself and here’s his take on stereoscopic zooming in the early days:

In the sixty’s, while I was attending Art Center and USC, I saw a couple of amateur 8mm dual camera 3-D rigs where the zooms were tied together via timing type belts and idlers and even one dual camera rig with push / pull lever zooms with the levers mechanically tied together by a cross brace.  One person also had a single zoom lens Bolex 16mm with the Bolex 3-D mirror box mounted on it.  These were sometimes shown at the various 3-D clubs in LA and info on them might be available in the UC Riverside’s 3-D archives.

The first time that I saw zoom lenses on a “professional” 3-D system would have been in the late 1970’s, at Paramount Studios, where Zoran Perisic [Zoeoptic] was demonstrating his zoom lens 3-D film system.  Zoran is best known for his matched zoom front projection work on the Superman movies and less so for his patent around the same time for electronically tying zoom lenses to dolly moves in order to hold a constant subject size while dollying.  In the 80s, I worked with Zoran in England on Disney’s “Return to Oz” and then later at Universal Studios.

My first use of a zoom lens on 3-D would have been at Heartland in 79 or 80.  We used a single six to one Cook zoom as a varifocal long body lens on single camera for dual pass mo-co miniatures on 3-D tests for Buck Rogers and Battlestar Galatcia.

Chris Condon, probably in the early to mid 80s, showed me a dual zoom 3-D system he had.

We tried matching zooms for a HD shoot on the Hines rig at Sony LA in late 80 / early 90s, but could not find two lenses that visually matched.  This was attempted after Sony Japan had done some side by side 3-D shoots that, while they had to wide of an IO, worked okay otherwise.

Slightly later, with Paradise, we shot a short 3-D film at Ed DiGiulo’s (of Cinema Products) house which even included a 3-D reverse zoom dolly shot.

Other things need to be taken into consideration, namely that the zero parallax plane that is use at the start of the zoom may not be the one that is best employed at the end of the zoom, and the same remarks can be made for interaxial separation. In other words, that which is desired to be at the plane of the screen at the start of the shot may now be required to be at some other Z location, and similarly, the strength of the stereo effect may need to be altered by smoothly and continuously varying the distance between the lenses. When zooming in on a subject, because of perspective considerations, the subject may tend to flatten out requiring a greater interaxial lens separation at the completion of the shot. All this would argue for interactive linkage of the ZPS (zero parallax setting) and t_c (interaxial setting) with focal length.

If you have information about this obscure but interesting subject – if you know anything about early attempts to do stereoscopic zooms – I’d love to hear about it. Right now, stereoscopic zoom defects or artifacts are usually cured in post. Vince Pace, in conjunction with Jim Cameron, has worked on stereoscopic zooms using high-def Sony cameras and Steve Schklair has camera and post-systems system at 3ality. Quantel has devised a post system that is now being used at FotoKem. All three outfits (Pace, 3ality, and Fotochem) are in Burbank. I’ve seen all demonstrated, and they can work great. The Quantel system is the first one off-the-shelf and any post-production studio can buy one, but Steve’s is proprietary. Points are picked at the beginning and the end of a shot, for example, and then the equipment more or less automatically rectifies the stereo pairs. What could have been a tedious frame-by-frame operation can now be automated. Let the machine suffer. In addition, creative, rather than corrective, decisions can be made about the placement of objects in Z space.

Obviously, zoom lenses that have centration or magnification artifacts aren’t suitable for real-time broadcast – for example, special events in Real D theaters. So work has to be done to solve the problem at the shooting end, and that might involve electronic correction with lookup tables and so forth and so on – which I believe I suggested in my patent.

Click here to download a copy of my 1983 Patent for Stereo Zooms