[MF3D.FORUM:1167] First roll run through the mystery Whutnik stereo

[Alan Lewis <3-d@xxxxxxxx>]

I just finished mounting my first roll through the Mamiya lensed MF
stereo camera project.

Brief observations:

1) All the exposures were perfect!  For a test roll this is great.  I do
not have the apertures or shutter speeds linked, and I mechanically link
the two lenses shutters.  (I used the Sputnik adj. link, it works
perfectly). 
I also use my trusty Knight Kit light meter (believe it or not, Knight
kits were like HeathKits in the '60's, and I built their light meter kit
then: used it ever since).

2) The vertical alignment of the lenses was perfect.  That surprised me.

3) The focus of each lens tracked very well.  From 6 ft. to infinity
they matched very well. This worked better than my first Yashica twin
project.

4) The stereo window is a bit too far away (probably 20 feet or so), but
it is no problem with using the Spicer mounts.  I'll remove some
material from the outer edges of each film gate.

5) The lens matching came out this way (lens focal length matching):
   a) I first calculated it by measuring the shims that Mamiya had used
at       the factory. One lens had shims, the other didn't.  I assumed
that       this equalled the f.l. difference between the lenses, and
then the       calculation came out to a .66% mismatch.
   b) On the roll of film I measured a vertical feature on each of two
L&R       images (using a loupe optical comparater).  The calculation
came          out to .64%.
So if you are comparing Mamiya TLR lenses for matching then you should
be able to just measure the shim pack the factory put in.  You would
subtract one shim pack thickness from the other and use this as the
mis-match.

One subjective note: This .66% mismatch between lenses is very good in
my opinion.  It does not affect the stereo image at all.  I had a
mismatch greater than this on my first Yashica camera project that was
used for my entries in the ex-Joel folio circuit. Did anyone notice a
problem with those images?

6) I got frustrated with the Sputnik leaf spring that applies tension to
the feed roll of the film.  It was way too tight on the film, I couldn't
even get the take-up spool to grab hold of the film and pull it
through.  I bent the spring back as far as I could, then I applied
teflon tape to the spring to reduce friction on the film paper.  Then I
gave up and grabbed my pliers and ripped that spring out!  It worked
fine after that.

An interesting note is that I had already run through a roll of Kodak
print film (I sacrificed it so I could study the film transport with the
camera open).  It did not have any problem with pulling through the
camera, even with that spring in place and the back closed.
It was when I used the Fuji Velvia slide film that it got very
difficult.  I can notice a difference in the friction value of the paper
backing.  The Fuji paper has more friction than the Kodak paper it
appears.

7) I used flocking paper inside the camera rather than a mask.  It
worked perfectly.

8) No light leaks at all!  What I did is to apply a thin strip of
flocking paper to the entire edge of the V shaped light trap protrusion
that fits into the trap groove (I applied it to the angled side).  And I
mean all the way around, even by the hinges. I also applied a strip
between the door edges where they butt together under the sliding
latch.  I painted all the door inside edges flat black, as well as the
metal overlap piece under the latch. You need a very steady hand, good
lighting and a magnifier to do all this.

Next I'll check out the flash performance of the camera.
-- 
Alan Lewis  
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