P3D Re: Twin rigs Flawed?

["Dr. George A. Themelis" <DrT-3d@xxxxxxxxxxxxxxxxxxxxxxxxxxx>]

Thanks Boris for a nice, solid summary of Twin camera rigs vs Realist
type stereo camera.  It is good to see an objective analysis of these
two techniques.

In my mind, there are two separate questions:  

1) Twin camera rig vs. Realist-type stereo camera

2) 2x2x2 (50x50x2, in metric) vs. Standard Stereo Format

You have assumed that a person who uses twin cameras is also following
the 2x2x2 format (for mounting slides), while the person who is using
a Realist-type stereo camera is also mounting their slides in Standard
Stereo format mounts.

How about me?  I am using both a Realist-type camera and single and
twin SLR cameras.  And I am mounting ALL my slides in Standard Stereo
format mounts.  And I know I am not alone!  I also know that there are 
stereo photographers who mount Realist slides in 2x2 mounts. 

If you accept that the (1) and (2) above are totally different issues
then we are in good agreement, except for the following minor points:

>-(Realist) Slide duping is more difficult and costly to obtain.

I don't think so.  You can mount your Realist-format slides in
2x2 mounts and they will be treated as 2x2 slides.

> -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.
    
As we have discussed before, this is your criticism of the Realist-format 
cameras and not the "Standard Stereo format".  My slides from my twin
rigs are perfectly orthoscopic in my Realist-format viewers. 
   
>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.

While what you are saying is true, here some more points to consider:
To get the closest spacing of the cameras you are restricted to vertical
portrait format, which takes away one basic advantage of full-frame
cameras, i.e. producing wide (landscape) stereos.  The curtains of each
camera are traveling in opposite directions which might show up in fast
moving action.  Staggering the cameras is not recommended for close
subjects.  If the subjects are far away, then you won't need the
staggering (I assume a bit of hyperstereo is desired in this case).

Here is my particular problem:  Because I mount my stereo slides in 
standard stereo mounts, if I use my cameras base to base them mounting
becomes tricky and I can only use Realist *size* mounts.  I enjoy people
close-shots, family, etc.  Hence the convenience of a standard stereo
camera is very desirable to me.  Notice, I said "standard stereo camera".  
I include RBT cameras (like the S1) in this group, not just a Realist.  
But I cannot include my twin Minoltas which have all the drawbacks you 
described.

-- George Themelis

PS.  Our club program next Tuesday is about 2x2x2 stereo slide projection.
The 2x2x2 system has found many strong supporters especially among those
interested in professional-quality stereo slide presentations (4 dissolve
projectors, etc.)  One of them is David Burder who has argued (rather
passionately) the merits of the 2x2x2 format in past issues of Stereoscopy.
(Note that 2x2x2 format does not exclude slides taken with a Realist-type
stereo camera.)  I am looking for information to put in an article for our
next club newsletter, regarding the 2x2x2 format.


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