P3D Re: Spacing problems with my RBT X4

["Greg Wageman" <gjw@xxxxxxxxxx>]

From: Alan Mahon <alanmahon@xxxxxxxx>


>All measurements were across the film plane.  When I say the apertures
are
>too close I mean the 24mm by 36mm rectangular openings inside the
camera
>which determine where images are placed on the film.

Well, that's not what you wrote in your original posting.  You
complained that the lenses were too close together.  Rod Sage and I both
read your posting the same way.  We simply mentioned that it is SOP in
stereo cameras for the lenses to be closer together than the film
apertures in order to set a window.  You obviously understand this, but
it wasn't clear in your message that you did.

>In the case of full
>frame RBT cameras the apertures should be 16 perforations apart which
is
>76mm.  This has nothing to do with creating a window in the camera it
is a
>function directly related to how much film is advanced each time.  A
window
>may be created in the camera by placing the lenses slightly closer
together
>than the apertures.

>There is a remarkable tolerance on the part of users of
>these cameras because the widest recommended mount has an aperture of
33mm.
>This misses the point.  Proper design would result in exposed film with
>images evenly spaced, indistinguishable from film from any flat camera
and a
>full range of processing options available.  What is surprising is RBT
work
>to a tolerance of 0.1mm to 0.4mm height adjustment being available with
>their mounts.  So why not get the camera right.


First, you over-generalize.  I have no problems having my RBTX2-exposed
film commercially processed and mounted.  There is a slight variance
between the frame spacing, but not, apparently, enough to cause the
average film lab any problems.  So the problem isn't universal, and RBT
do, at least occasionally, "get the camera right".

Second, uneven spacing isn't unique to RBT stereo cameras.  See the
wealth of postings, including very recent ones, about variable frame
overlap in Realists (and Reveres and...).  Even mono SLRs can have
problems with uneven advance, and there's only a single mechanism at
work there.

I personally am amazed and astounded that ANYONE can cut apart two
sophisticated, modern electronic SLRs like the Ricoh KR-10m, weld two of
them together and have them work flawlessly, totally synchronized, in
addition to successfully modifying the electronic advance to the 1-3-1
sequence required for the format.  I wonder sometimes if people besides
Sam the Hacker really appreciate the technical challenges involved?

There's an old saying about the dancing bear that comes to mind.  "The
wonder is not in how well he dances, but that he dances at all."  Except
in the case of RBT stereocameras, for me the wonder IS how well they
dance!

     -Greg W. (gjw@xxxxxxxxxx)