P3D Re: '54 Vintage Bolex 2D 3D H-16 Stereo Movie Camera

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

Norm Lehfeldt, in response to Dan Vint's inquiry, wrote:

> This was actually a beam-splitter system that fit most Bolex 16mm
> cameras. It came with a projection lens what was actually two lenses
> with polarizers in a single barrel. There were sleeves to fit most
> standard 16mm projectors. I have a similar system made by Elgeet. It
> works pretty well if you like the vertical format images it produces.
> 
> I have heard the the Bolex polarizers have usually gone bad and must be
> replaced. My Elgeet ones are fine.
> 
> They are a little higher relative to width than the pictures produced by
> the 35mm beam splitters because the 16mm frame is relatively narrower
> than the 35mm frame.
> 
> Norm Lehfeldt
 
Norm and Vint,

I own one of these Bolex outfits that I bought back in the 50's when I
was in the Air Force. Norm is partially right in that the unit has
prisms attached to the lens mount in a manner similar to the Elgeet
(which I have also used). But the Bolex system has the advantage that it
is not, strictly speaking, a "beam splitter" in that it uses two very
tiny, extremely short focal length lenses (coated 12.5 mm f/2.8 Yvar)
mounted side by side in the 16 mm "C" mount, rather than using the
prisms to "split" the image seen by a single lens. Behind the lenses is
a thin, vertical, black septum that keeps the two images from
overlapping on the film.  Like the Elgeet, this produces two vertical,
side by side images that make up the stereo pair within a standard 16 mm
frame, but the images are, unlike the Elgeet, untransposed. Accordingly,
you cannot intercut scenes made by the Elgeet with scenes made by the
Bolex -- you would have to turn your Polaroid glasses upside down to
view the Elgeet scenes if you were projecting them with the Bolex
projection lens.  

The Bolex has other advantages:  1. It has no problem with dividing
lines between the pictures;  the Elgeet, as you stopped down, gets an
increasingly wide, black dividing line between the pictures that ate
into the available picture area, and at larger openings reduced to the
point where the images could overlap slightly.  2. The Bolex has an
available attachment, with prismatically toed-in close up lenses, for
two ranges of close ups.  This is very convenient, as it enables you to
bring the close-up lenses into position simply by turning a knob on the
circular housing attachment. (I have this also, and it works quite
well.)  3. As I recall, the Elgeet also has some slight, unavoidable
keystone distortion at its closest focusing distances, that does not
occur at the same distances with the two-lensed Bolex system.

Norman is right about the Bolex projection lens and its polarizers.  Dr.
John Hart, honcho of the  SCSC Movie/Video division, helped me replace
mine several years ago.  It is not too difficult to do once you obtain
optically flat, heat resistant, polarizing material that you can cut to
a small size.

I am not intending to criticize the excellent and inexpensive Elgeet
system; I am only trying to point out that the Bolex was a more
optically sophisticated system that got slightly better results at a
higher cost.  The Bolex was a nicely made system that worked moderately
well, provided that you had a bright enough projector.  For their day,
Bolex or Elgeet was the only way to go for motion stereo, and it was
tantalizing to see in them the possibilities for the future, now
realized in systems like 3D IMAX.  Too bad that 16 mm film and
processing was always so expensive -- I couldn't afford much film on my
Air Force enlisted man's salary, and inflation and the fading of amateur
interest in 16 mm finally put the film and processing costs out of
sight.  Field sequential stereo video is where it's at, today, for us
budget minded amateurs!

Cordially,
Oliver Dean