Re: PHOTO-3D digest 2337

[P3D <JNorman805@xxxxxxx>]

In a P3D, Steve Berezin asks Ruben:

<< Did you use a special technique to match the zoom magnification of the
 two cameras? I would think that this would be the hardest part of
 matching the two pictures.  I though it would obviously be easier with a
 fixed lens.
  >>

I don't know how Ruben does it, but I also use a Canon EOS Rebel twin rig
with 35-80 zoom lenses, and here's what I did for just about perfect matching
of the focal lengths through the zoom range:  I mounted the cameras bottom to
bottom via their tripod sockets in a home-built wooden frame.  I used
shoemakers' cement to glue a band of toothed belt around the barrel of each
lens.  I glued the same band material around the circumference of each of two
nylon wheels that I picked up in an industrial junk shop on Canal Street in
NYC.  The wheels contain intergral roller bearings in a race with a 1/4 inch
shaft opening.  I mounted the wheels to the wooden frame, via 1/4 inch bolts,
so that their toothed surfaces meshed with the toothed surfaces  of  the lens
barrels (one wheel above the lens barrels and one below, for positive
meshing).  I placed a large rubber band around the lenses to increase the
pressure between them and the toothed wheels.  Thus, when I turn one lens
barrel to zoom, the other automatically travels right along with it.  As long
as I set the lenses up so that they both start at the shortest or the longest
setting, the zoom range matches perfectly throughout.  Hope this helps.
                                                               Jim Norman


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