7P Realist

[P3D John Slivon <frogs@xxxxxxxxxx>]

My 7P Realist is the result of wanting a 7P format stereo camera but not
being able to afford either a Verascope or a Belplasca.  Another Realist
that I have had problems with the flash and after opening the top to fix it
I discovered an empty attic(so to speak). I made a few sketches and
determined that I could install a set of gears into that space to regulate
the 1-3 progression.  

Next came the search for suitable lenses. I wanted Leitz Summarons but ran
into the $ issue. I settled on a pair of unblemished 35mm 3.5 Rikenon lenses
from  two junk Ricoh AF-70 point-and-shoots that I found in a St. Paul
camera store for $6. These are very nice lenses based on a highly compressed
Tessar design.

With a minor amount of machining all three Rikenon cells dropped into the
space that the two forward elements of the David White triplet occupied. The
rear portion of the lens mount was machined away to get the lenses as close
to the shutters as possible. Some major machining of the lens mounts was
necessary to achieve this end.

For the progression mechanism I used  two steel gears, .75" diameter and
.25" diameter (32 D.P.).  The larger gear free-wheels around a post that is
attached, through a slot in the camera body, to the focusing plate. This
gear has a steel washer brazed to it that has two small slots cut in its'
edge at 90 degrees to each other.  These slots are the stops for the 1-3
progression.  The smaller gear replaces the gizmo that used to be directly
connected to the 10 tooth sprocket. (The gizmo has the stop slot and the cam
that activates the frame counter.)  As the take-up spool pulls the film
across the 10 tooth sprocket, the gears meter out first 7.5 perforations and
then 22.5 perforations and then repeat the sequence.  It's not a perfect 7p
but it's close enough.

I get no overlaps and get 20 pairs to a 36 exposure roll of film. The frames
are 31mm wide and fit very nicely into an RBT-7 mount.
 
This conversion was relatively straight-forward.  Modifying the lens mounts
was very tedious.  I did all of the work myself using a very small lathe and
a milling attachment that I made for it. (I did need to use a Bridgeport
Mill once on the body because my milling attachment is too small). I was
able to retain the f-stop rings and all of the other features of the
Realist. With the lens cover opened, the only difference is the slightly
sunken look of the lenses.

By the way, the picture quality is superb.
John R. Slivon


------------------------------