P3D RBT choices

["David W. Kesner" <drdave@xxxxxxxxxx>]

Everyone who has posted about their RBT cameras have all had 
the full frame 24x36mm B option. I believe that Jon said 80-90% of 
all RBT's sold are this option. Well, I chose the 24x33mm A option 
and I would like to explain why.

First is the inter lens spacing or stereo base. The A option is 
65mm and is near ortho for most people. To get full frame with 
65mm spacing you only get 13 pairs from a 36 exposure roll (as 
compared to 20 pairs for the 24x33mm). This by the way is the C 
option on the X model RBT's. The full frame B models have 75mm 
spacing give a slightly hyper shot. A lot of people don't really notice 
this, but it is very evident to me. The 49mm spacing option of the 
S1 is too hypo for me (although great for close-ups, especially 
underwater). The 59mm option of the S1 is also slightly hypo, but I 
don't know if I could tell as I have never seen a shot from it except 
for Dr. T's in Stereo World.

With the 65mm base I have been able to shoot as close as 18 
inches and get a shot that looks great in either a viewer or 
projected (with the zoom at 70mm that is a pretty small area). You 
just have to be very careful to limit the total distance so as to not 
get objects in the background with too much parallax. Most of 
these can be mounted in a 7p closeup (23x26mm) mount with a 
few needing a 5p. I have never had to go to a 4p. By the way, the 
7p closeup mount is only available in Spicer mounts.

The other reason is that I wanted to be consistent in all my 
mounting and be compatible with the most universally accepted 
format. That would be the 41x101mm mask with a maximum 7p or 
23x28mm aperture opening.

Now, by universally accepted I mean by commonly available 
equipment such as viewers and projectors and requirements of 
exhibitions and folios such as PSA, SSA, etc. What I mean by 
commonly available equipment is what I would find at any stereo 
club meeting, or the home of most any stereo photographer. Yes, 
2x2 format equipment is available and probably the choice of 
"professionals", it is just not that common amongst "recreational" 
stereo photographers which make up the majority. And what they 
have are Red Button and equivalent viewers and TDC and 
equivalent projectors.

Now, by consistent mounting I mean that I want to be able to sit 
down with a roll of film and mount everything the same way in the 
same mount. I don't want to have to set the good ones aside to 
mount differently and sure don't want to have to mount one way and 
go back later and unmount to mount in another mount for an 
exhibition or folio.

I can understand some people wanting the convenience of having 
their slides mounted commercially and I have nothing against that. 
Anything that will get more people involved in stereo photography is 
great. However, it only takes 30 minutes to accurately and 
consistently mount a roll of stereo slides. It probably takes longer 
than that to go through all your commercially mounted slides and 
pick out the ones you like and then remove them from the mount 
and remount them to be able to project or enter in exhibits and 
folios.

Sorry if this was too long!


David W. Kesner
Boise, Idaho, USA
drdave@xxxxxxxxxx


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