P3D Re: Zoom lenses

[JNorman805@xxxxxxx]

Rolland Elliott asks:

<< Has anyone tried using two 35mm SLR's with identical zoom lenses on
 them to take 3D pictures?  I would think this would be very
 convienient for taking a variety of pictures.  However, I wonder if
 one runs into problems making sure that both of the zoom lenses are
 set at the same focal length.  The identical focal length would be
 easy to achieve for the longest and shortest forcal lengths, but
 accurately getting the middle focal lengths would be difficult. >>

Yes, Rolland, I use 35-80 zoom lenses on my Canon EOS Rebel-X twin rig.  The
cameras are mounted bottom-to-bottom on a wooden frame, so that the actual
space between the camera bottoms is the 1/2-inch thickness of the wood.  The
lenses are arranged to operate in tandem as follows:  I cemented segments of
toothed industrial belting around the zoom ring of each lens.  I cemented
segments of identical belting around the circumferences of two 1-inch nylon
roller bearings.  I mounted the roller bearings on 1/4 inch bolts, which are
screwed into the front of the 1/2-inch wooden frame in such a manner that one
roller rides above the pair of lenses and one rides below. The teeth of the
lenses mesh with the teeth of the rollers. I wrapped a band of elastic
material from the notions department of a fabric store around both lenses, to
keep them in firm contact with the rollers.  When I rotate one zoom barrel,
the other follows right along.  As long as both lenses are zoomed all the way
in (or out) at the starting point, they are at the identical in-between point
at all times.  From time to time, I check to make sure one lens or the other
hasn't jumped teeth.  So far, they never have.  It's simple, a hell of a
conversation piece, and it works.  Hope this helps.
Jim Norman


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