P3D Re: Twin rigs Flawed?

[boris@xxxxxxxxxxxx (Boris Starosta)]

"Twin rigs Flawed?"

I hope that this posting will be of particular use to beginners, who are
pondering many technical issues as they decide upon the purchase of their
first stereo camera.  The title of this text is a play on a very feisty
thread some weeks ago, entitled "Realist system flawed?",  that has lead us
to consider in a balanced fashion the advantages and disadvantages of
shooting stereo slides with either a "twin rig" (two 35mm cameras mounted
together on a bracket) or a "Realist" format camera.  In corresponding with
several other people, who have contacted me recently with questions
regarding the initial setup of a twin rig, I rediscovered that my own twin
rig was not put together without some difficulties.

It is understood that customization of equipment is an option for both
modern 35mm cameras, Realist cameras, as well as the viewers needed to
enjoy your stereo slides.  However, for the purpose of this comparison,
which is aimed at _assisting the novice_ in making a decision among _lowest
cost options_, we assume minimal customization of the equipment.  (Of
course, a twin rig represents a minor form of customization in and of
itself.  But here we assume twin rigs comprised of standard cameras).

This comparison assumes you are shooting for
stereo slides.  Some of the points will also apply
to those who wish to shoot for stereo cards.

Twin rig drawbacks:

Difficulty / cost of initial setup, purchase:
-if you start with zero cameras, it will likely
   cost more to set up your rig (than a Realist camera).
-Unless you make your own bracket, expect to
   pay $50-$100 just for that. It's easy to make
   your own, however.
-you need to match lens f.l.
-you need to match lens apertures
-you need to match camera body shutter speeds
Thus, setup of a twin rig takes some time, and an
understanding of optics, cameras, and stereo.
Also maybe some service work by a dealer,
unless you buy new cameras.

Difficulty during "slide production":
-synchronizing shutter requires twin release.
   Difficult with flash, unless cameras are electronic.
-weight and bulk: even small "Point and Shoot" (P+S)
   twin rigs are going to be relatively big.
-handholding is very difficult, unless your rig
   uses two fully automatic cameras.

Twin rig advantages:

Ease of use / flexibility during "slide production":
-You can twin fully automatic cameras.  Shoot easily with
   auto exposure, focus, wind, etc.
-At least you can get a light meter in the cameras.
-you get a choice of f.l. lenses.  Use zoom, carefully.
   (Although we advocate shooting just 50mm
   for regular pictures.)

The 2x2 format stereo pairs produce superior views, and
make for easy "post-production":
-you can get very large views in an inexpensive viewer
   (orthoscopic if you shoot w/50mm lenses).  Apparent image
   will be up to twice as large as with cheapo Realist viewer.
-if you toe in judiciously, you get slides back that are instantly
   useable in a viewer.  No remounting needed.
-No remounting means less cost and time spent in "post-production"
-Duplication of 2x2 slide pairs is relatively easy.


Standard American Realist format drawbacks:

Possible difficulties/risk in initial purchase:
-the camera will be old.  Might be in need of overhaul.
   Probability of mechanical bugs is moderately higher than
   with twin rigs using modern and new equipment.

Difficulty during "slide production":
-the older cameras are not automatic.  The Realist does not have
   a light meter in the camera.  (I don't know about the others).  This
   will be important to snapshooters who don't want to mess with
   determining and setting exposure and focus manually.

Difficulty / cost in "slide post-production":
-Obtaining finished and mounted stereo pairs from a processor
   is comparatively difficult and time consuming.
-If you shoose to process in a regular lab, film from a Realist
   type camera must be returned from the processor uncut,
   as a long strip.  You must use a film cutter, and mount the two
   appropriate "film chips" in a Realist format stereo mount.  Although
   mounting gets easier and faster after you learn it, it still takes
   _some_ time.  Cleanliness and careful film handling are important.
-Mounting supplies cost some money.  Easiest to use mounts (such as RBT)
   will add considerably to the cost of each slide.
-Slide duping is more difficult and costly to obtain.
-Quality viewers are quite costly, and still do not supply a view that is
   orthoscopically correct.  (i.e. there is slight spatial distortion)
-Inexpensive viewers will give a smaller and spatially distorted view.


Standard American Realist format advantages:

Portability / reliability during "slide production":
-The Realist camera itself is very robust.  Other cameras in the format
   perhaps less so, but probably still better than most twin rigs.
-Any Realist type camera will be far more portable.
-Although manually set, focus and exposure will be synchronized.
-Flash synchronization is no problem.
-Handholding is no problem.

Realist advantages in "post-production":
-Realist format slides are universally recognized and accepted _within
   the community of stereo enthusiasts_.
-Most competitions accept only Realist compatible slide mounts.
-Only within the Realist format can you obtain commercially made high
   quality viewers.  Inexpensive 2x2 slide viewers give a good quality view
   because of the larger size of the slide and better focal length matching.
   But the best optics are found in Realist compatible viewers
   (such as the Red-Button).



Summary:

Get a Realist type stereo camera, if you want a compact, robust camera, and
don't mind paying a bit of money for a good image in a superb viewer
(Red-Button).  It will not be possible to obtain a truly orthoscopic image,
unless you customize either the camera or viewer.  Cheap viewers for this
format are disappointing because of small image size, and a distorted
(stretched) spatial field.  This is the camera for impromptu family and
vacation picture taking.

Go for the twin rig, if you intend to distribute your slides to others
without their own viewers.  This might be the case for serious hobbyists
and artists.  Duping will be easier, and supplying decent viewers to those
who will receive your slides will be far less costly.  Although the images
obtained in these viewers may not be optically perfect, they will be larger
and truly orthoscopic, if you shoot with 50mm lenses (Notwithstanding its
name, the "Pinsharp" viewer is slightly blurred here and there, and has
some chromatic aberration).



Additional comments and sources regarding the 2x2 format twin-rig:

It is often said that the photographer cannot get the correct interocular
(i/o) spacing, when shooting with a 35mm twin rig.  I disagree.  Shooting
with two older style SLRs (i.e. they are not exactly small), mounted base
to base (vertical portrait format), I get the same i/o spacing as the
Realist: 70mm.  If you shoot with your two 35mm cameras mounted landscape
format (horizontally), you can mount them staggered, one behind the other,
to get _close_ to standard i/o spacing.

The Pinsharp viewer can be obtained from Reel-3D Enterprises.  Look at
<A HREF="http://www.stereoscopy.com/reel3d/slide-viewers-twin.html">

For a very inexpensive twin rig, great for learning and experimenting, look
at Kouno's page
<A HREF="http://www.rpm.or.jp/home/h-kouno/3dphoto.htm">



Respectfully submitted,



Boris Starosta

usa 804 979 3930

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

"Ortho über Alles"

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