[photo-3d] Tri-Delta Prism stereo attachment

[Peter Davis <pd@xxxxxxxxxxxxx>]

I've continued to play around with the Tri-Delta Prism stereo 
attachment.  I now believe that this is a very well-designed and 
manufactured item.  It give true stereo images through a regular 
range-finder or SLR camera, and the overall quality is excellent.  There 
are, however, certain quirks:

Viewer
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I think the viewer is the weak link of this system.  It's small, gives very 
low magnification, and has a diffuser which adds a visible "grain" to the 
image.  I'd love to try to build a better viewer for this system, but I 
don't really know where to start.  Has anyone ever tried or heard about 
something like this?

The other problem with the viewer is that because it is so small, you don't 
get the sense of being enveloped by the image as you would with a larger 
viewer.  I think there's too much peripheral vision left open.  If I ever 
build a viewer, I'll try to solve this too.

I've actually tried cutting some of these slides in half and mounting them 
in horizontal half frame mounts (from Paul Talbot, by way of Don Parks ... 
Thanks VERY much, guys!!!).  The results are excellent!  They produce 
really good pairs, when viewed in my Eckeren viewer.  This makes me think 
that a really good, lighted viewer with good lenses would be a great asset 
to this system.

Vignetting
----------
In my tests, I get some vignetting at the bottom corners of the image.  I 
suspect this may be at least partly due to the fact that I don't have the 
original adapter rings, so I have to use a pair of step-up/down rings which 
spaces the unit about 3mm further from the lens than it should be.  I'd 
love to find one of the original rings, or at least a machinist who could 
make me something like it.

Grain
-----
Because the system splits a regular 35mm frame, the individual film chips 
are smaller (ie, grainier) than larger format stereo images.  They're 
actually not much smaller than Realist chips, but they're near the 
borderline for acceptable (to me) grain for Kodachrome 64.  I'm wondering 
if anyone's every tried to build a stereo attachment like this for a medium 
format camera.

Projection
----------
The Tri-Delta system includes a projection adapter which allows you to use 
the taking attachment to project these slides.  Basically, you put the 
Tri-Delta on your project lens somehow, and then put this device on 
top.  It's basically a 45 degree angle mirror and some polarizers.  I've 
never tried this, so I can't say how well it works.  There's some kind of 
plastic ring meant for putting the attachment on a projector lens, but I 
can guess how it's supposed to work.

-pd
--------
                                 Peter Davis
                  Funny stuff at http://www.pfdstudio.com
                  "The artwork formerly shown as prints."