P3D Stitz vs. Stereo-tach (beamsplitters)

[SHIELDS@xxxxxxxxxxxxxxxxxx]

Ridiculous? Not in the same class? But I'm comparing the Stereo-tach
instead of the Pentax (which I use for 'normal' work) because its
inner mirrors are more closely fitted at the center and create less
of a dark band when stopped down--better for small apertures for closeups.
I know it's tough to fit an adapter to, but once it's done, it's done, 
and I paid only $60 for mine. The front-surface mirrors are first-rate.
Other than that, my remarks could apply equally to the Stereo-tach and 
the Pentax.

I got my Stitz today (and now I have both it and the Franka, which will
be better for telephoto because of its wider stereobase at 110mm, once
I install the front-surface mirrors I have acquired). It _is_ a very 
nicely made unit, with smoothly operating controls, except that mine has
a lot of lash in the curtain (it isn't a diaphragm despite the designation,
as Ben Melton pointed out to me) control at one end. I can understand how 
anyone could become fascinated with it for that alone.

However, it has certain definite drawbacks. The mirrors are ridiculously
small compared to the Stereo-tach. I can see this would create problems
if I used it with a 50mm lens (which I don't plan to do). For this reason,
and because it is so large and heavy, I would never use it for general
shooting. (It does have a standard 70mm stereobase--this works against good
telephoto shots even though the mirrors will diverge to handle a 300mm
lens.) I suppose the small mirrors were a compromise to make them adjustable
with the nice control mechanism without making the whole device _too_
large. The mirrors _will_ converge into the range of a +3 closeup lens
using an 85mm lens. This is better than the Stereo-tach, which has no
adjustment for mirror convergence--it will handle only a +2, and at only one
distance. But to get really close, I'll have to go to a much longer lens
and/or use a tele-converter. Finally, the "mysterious adapter ring" thing
really isn't. Mine, at least, has a 52mm male thread. It came with a 
straight 52mm to 52mm adapter ring--it just spaces the beamsplitter
out from the lens. I threaded on an ordinary 52mm to 49mm adapter, readily
available at any camera store, in its place, which worked beautifully and 
at once allowed me to mount it to my 49mm-threaded lens.

I wanted to remove the cover glasses from the front because I felt they
would unnecessarily degrade the images. Some previous owner had already done
this (the glasses came with it)--it simply requires the removal of two
screws from each slip-on retainer ring. (Don't know about the cover
glass in back yet.)

I think I might be happier with taking the Stereo-tach out in the field--
so much smaller and lighter, and use the Stitz only when really necessary
(which something often is at the outer limits of photography).

While the Stitz has its limitations, I'm happy to have it and think it will 
prove a useful tool in extreme closeups. But it isn't worth some of the 
inflated prices that are seen.

I'll just add that I stick with the beamsplitter format because of:
(1) use of a really modern, but low-cost camera behind the beamsplitter 
(2) choice of focal lengths, again at low cost
(3) low film/processing cost with the 18X24mm images
(4) extreme ease of mounting the pre-attached, pre-transposed pairs
I use a viewer only, which eases or eliminates any mounting errors
or keystone distortion--no plans to project my images.

Mark Shields

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