P3D trouble setting up Twin SLR.

[boris@xxxxxxxxxxxx (Boris Starosta)]

This responds to a private inquiry from David Tiede regarding how to go
about getting a twin rig set up.

Hi David:

>each.  I did a quick search on the internet but only found such cameras
>for $110 or more.  Thus my question to you:  What do you know about an
>SLR camera sold by Cambridge Camera Exchange?  It is called the Cambron

I don't know anything about it.  The important things to look for, once you
get them in your hands, are that the shutter speeds are well matched, and
that the apertures and f.l.s of the lenses are well matched.  I was
surprised by the variability among seemingly identical cameras.  Really, I
recommend you find a dealer in used cameras, who will put up with your
trying out several of his cameras and lenses to find a matched pair.

It's a lot of variables to match up, and it took me several hours of
fiddling in the showroom of the dealer that I have here.   I tried out a
bunch of Pentax K-mount cameras (K1000s), some of which were made in Japan,
others in the U.S., leading to slight differences.  Even the year of
manufacture made a difference!  After finding a pair whose shutter speeds
matched well, both made in Japan, I discovered that the viewfinder optics
were not matched.  Granted the taking lenses would be matched, and the
framing on film identical, but the view through one camera had an apparent
field that was of a different size.  It surprised and bugged me.  So I
didn't set up that pair.

You'll be surprised how much variance there is in the f.l. of lenses, too.
I had seven Pentax 50mm f2 lenses to choose from, and each one produced a
different size image at the film gate!  Not only that, but the camera
bodies mattered too, to slight degree.  So when I found a pair that was
close on the two bodies, I swapped them around, to see if that was not even
better.  I judged the image size right at the film gate.  Lens on camera,
camera back open, pointing at a flat wall with lots of different things on
it.  Used a ground glass and loupe on the film gate.  Saw to it that
exactly the same things are recorded at the film gate (the cameras are best
aligned on your twin rig bracket to do this).

When matching lenses for apertures, I paid most attention to f16 and f11,
of course.  I just judged it by eye, looking through the lens, although
your dealer might have a way of measuring it.  My pair of lenses don't
match well at around f4 for some reason, but a good match at the smaller
apertures was more important for stereo.  The dealer should have a way to
measure shutter speeds on the bodies also.

I did all this after I had already bought a second SLR off of a friend.  So
by the time I went to a dealer (who I was told was a rather standoffisch
aloof person) to set up my rig properly, I had already shot some stereo
pairs (with imperfections caused by this and that being mismatched).  I
brought all of that in, and immediately aroused the curiosity and interest
of the dealer, who knew little about stereo photography.  Over the next two
visits, he helped set me up with two matched bodies and lenses.  I traded
in the lenses and bodies I had brought in.  That's probably a lot better
way of doing it, than just showing up with ideas in your head.

>How important would it be to you whether the normal lens were 50mm,
>55mm or 58 mm?  The normal lens for the Pentax Spotmatics was apparently
>55mm.
>
Ha, ha.  Well, if you've followed the thread on "Realist Flawed,"  you know
I'm going to insist on matching the viewer optics.  However, to go to a
little longer lens is not going to be big problem, and may even help your
portraits a bit.  50mm is the f.l. of inexpensive 2x2 viewers.  I don't
know what your Wollensack viewer has, although I imagine, as a Realist
format viewer (?), it will have a shorter focal length.

As far as speed of the lens goes (f1.4 vs. f2), the faster lenses are
always a bit pricier.  You don't need the extra speed, so why pay more?
It's possible that the better optics of an f1.4 might also improve the
image quality at f16, but I doubt it.  My lenses are inexpensive f2s.
Pentax lenses.

By the way, the Red-Button cannot view 2x2 slide pairs.  You may have been
led to think so in my thread re. "Realist Flawed."   To view 2x2 pairs in a
red-Button, you unmount the film, and re-mount in a standard Realist-type
stereo slide frame.

Good Luck,



Boris Starosta

usa 804 979 3930

boris@xxxxxxxxxxxx
http://www.starosta.com
http://www.starosta.com/3dshowcase

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