[photo-3d] Re: Are beamsplitters crappy?

[Mark Shields <beamsplitter@xxxxxxxx>]

In a word, NO!  :-)

Seriously, there were two kinds of beamsplitters discussed in
this thread so far, a "real" beamsplitter, which actually takes
light and sends it in two different directions, and a "stereo
adapter" like the Pentax, Stereo-tach, Franka, Stitz, etc., 
which fits on the front of a 35mm SLR (or other camera, if
your adventuresome!) and uses mirrors to place a stereo pair
within a standard 24X36mm aperture.

I'll speak to that, since I don't use the other kind! My kind
of beamsplitter images _are_ vertical, not horizontal, but
the term "skinny" isn't fair since the ratio of width to length
(18X24) is actually better than with a full 35mm frame (24X36).
It has long ago been commented that half-frame (which is what
beamsplitter images are) 35mm pictures are easier to fit to an
8X10 print than full-frame, for this reason. As to being vertical,
there are certainly times when I would like to go horizontal, but
I found that I have shot a lot of vertical images myself, and just
have to deal with it. On the other side, you can't shoot a vertical
picture with European format cameras, or with the usual 35mm twin
rig (I know you can shoot verticals if you have the bracket for it,
and there are some clever ones that let you switch).

Beamsplitter images are nice and sharp--no problem there (except
for ghosting with the second-surface mirrors in the Franka). There
is some linear distortion introduced, called "keystoning." It is
minimized by the Pentax viewer. But I have heard that beamsplitter
pairs have been successfully projected as well. I have been able
to fuse these O.K., as have almost all of the people viewing my
slides.

In picture taking you are also restricted to certain f-stops,
to avoid the dread black band. 

But in return you can have full exposure automation and reflex viewing
and focusing, plus excellent film and procesing economy.

Different? Unusual? Not to your taste? Maybe. But not crappy.

Mark Shields

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beamsplitter@xxxxxxxx
http://www.stmattpitt.org
"Whoever welcomes a child in My name welcomes Me," Jesus said.
"Whoever welcomes Me welcomes not Me but the One who sent Me."
  -Mark 9:3

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