Re: Split frame 3D home movies.

[P3D Oliver Dean <3d-image@xxxxxxxxxxxxxx>]

Marvin Jones wrote:
> > RE: Don Radovitch wonders if beam splitter on camera and projector 
> > with Polarizing filters is possible. Except for the simple mirrors 
> > (prisms are preferable), Paillard Bolex had such an accessory for 
> > their cameras and an outfit is probably in the used market at 
> > collector prices. At least the ads and literature might be found in 
> > old magazines and at camera swap meets. BobH
> > 
> Elmo also offered a 3D attachment for their Super-8 camera and projector
> shortly before video came along and wiped out "home movies" on film. I
> think the Elmo system was somewhat preferable to the Bolex (other than the
> fact that the Bolex was 16mm, which was technically superior). The Bolex
> system split the standard frame down the middle vertically, giving you a
> "door frame" image that was taller than it was wide, which seemed really
> strange since we are used to movies being landscape format. The Elmo system
> also split the frame the same way, but contained a series of prisms that
> turned the images 90 degrees and put them on the frame sideways, "foot to
> foot". The resultant image was just about the same format as a standard
> movie.

It should be worth mentioning that the Bolex system had one excellent
advantage:  It used two, separate, matched 25mm lenses behind the mirror
assembly, each with its own f/stop linked to a single control for both
apertures.  This eliminated some keystone distortion and reduced the
variation in width of the center dividing line when you changed f/stops,
as compared to single-lens split frame systems, such as the Elgeet.
However, the twin lens assembly protruded so far into the camera body
that the Bolex slide-in filter system could not be used (a special,
empty holder had to be used to prevent light leaks).  This limitation
required that, if filters were needed, series V filters would have to be
attached to the outside of the prism housing, which could cause some
vignetting.  

The lens turret had to be locked with a special screw cap at one of the
lens positions to prevent accidental damage to the stereo lenses.  The
lens assembly was rotationally aligned by a special fitting on the
turret hub, which slid into a slot on the side of the prism housing and
kept it from rotating out of perfect alignment with the aperture
baseline. The Bolex camera models with through-the-lens focusing could
not be used, because a 45-degree angle, partial reflector, which stole
the  light for the focussing system, prevented the stereo lenses from
being inserted all the way into the lens cavity in the camera body. But,
when properly installed in the right model, the system was solid and
reliable.  Mine has the useful accessory close-up attachment wheel,
which provides two sets of prismatic close-up lenses for different
distances, as well as an empty position for normal, non-close-up use.

For projection, a special split-lens projection lens with split
polarizers was used, via adapters, with most popular models of
projectors then available. No mirrors or prisms were used in its design.
Use of the lens with a more modern 16mm Bell and Howell requires that a
special adapter be fabricated.  Once the adapter is made, quick, solid,
and reliable adjustment of the special projector lens is possible for
vertical error and focus.  No horizontal adjustment is possible. 

The Elmo, although spectacular when adjusted correctly, was a bear to
adjust and rather delicate, I understand. I believe some of the more
succcessful units were redesigned and rebuilt with more rugged parts. 
We have had some excellent films made by both systems showed at the
Movie/Video Division of the Stereo Club of Southern California, but the
Bolex system seemed generally easier to set up and adjust.

The maker usually had to set up and adjust his Elmo films, while others
could usually set up and adjust the Bolex and Elgeet films.  Both
systems provided satisfying results when properly adjusted, with the
Bolex providing the less desirable format but a brighter, slightly
sharper image.

Cordially, 
-- 
Oliver Dean -- 3d-image@xxxxxxxxxxxxxx
Dominguez Hills (near Los Angeles), Calloushernia, USA


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