P3D The power of a millimeter

["George A. Themelis" <DrT-3d@xxxxxxx>]

Bob_Maxey@xxxxxxxx wrote:

>I hardly think the designers of the RBT are unaware of how stereo 
>cameras are / should be designed. As for 1mm - that is a tiny number 
>to be worrying about. 

I need to remind you Bob that 1.2mm will bring the stereo window from
infinity to 7 ft in a Realist camera.  So if the film gates of the Realist
camera were off by 1.2 mm and were spaced at 70mm instead of 71.2mm, then
there would be no window built into the camera, plus a frame overlap.  A
disaster.

You seem to be saying that this 1mm difference in RBT cameras is a matter
of tolerance.  If that was the case, there would be cameras around with
proper film advance (I am not aware of any).  Seems that RBT are very
accurate in reproducing what they are making now and the fact that they
quote the lens spacing to 75mm makes me suspicious.  It would be nice if we
could get RBT's ideas on this issue.

>The only way any problem could be determined is by testing the hypothesis 
>that a silly little millimeter makes a difference.

If you think about the issue (as Alan and I have done) you will see that
this is a fact an not a hypothesis.  One "silly little millimeter" does
make a difference in the spacing of the frames in the RBT cameras.  About
the spacing of our eyes being variable, this is a totally different
problem.  The 1mm in the spacing of the film gates of the RBT cameras
affects the film advance from a mechanical point of view.  It has nothing
to do with the physiology of seeing stereo.

>The Stereo Realist is a big, bulky, uncomplicated camera that is most 
>certainly not designed to great tolerances. 

There are parts that need tight tolerances and parts that don't.  Wherever
tight tolerances are needed these are obtained.  But the design of the
camera is such that tight tolerances are not needed for the most part.

George Themelis