P3D Re: RBT X3A lens spacing

["Greg Wageman" <gjw@xxxxxxxxxx>]

From: David W. Kesner <drdave@xxxxxxxxxx>


>With the 65mm lens spacing I am able to get more of an "ortho" view
than the slightly hyper >75mm spacing.

Have you measured your own interocular?  Mine is closer to 70mm than to
65mm, so for me a 65mm spacing is ever-so-slightly HYPOstereo.  I wonder
how much the demographic shifts in the U.S.A. would affect this choice
of "average" interocular since the original market research was done
over 50 years ago now?  (For example, I know that people in general are
considerably taller, on average, than they were during colonial times.
Are our eyes wider, too?)

>I can get two more pairs from every roll of film. I mount in  standard
7p mounts which are the >largest universally accepted format.

"Universally accepted"?  Define please.  There are many stereo
projectors which will not project a 7-perf slide in its entirety without
modification, and I seem to recall mention of some that won't do it at
all.  And certainly twin 2x2's won't project any Realist mounted slide.
The Realist Red Button needs modification to fully view 7-perf slides.
This doesn't sound very "universal" to me.  If there is such a thing at
all, I think it would be the 5-perf Realist standard, although I could
argue that 2x2's are more "universal" because besides being currently
manufactured and readily available from many commercial sources, there
were probably at least an order of magnitude more of them made and sold
than stereo projectors.  (But they are not nearly as common in stereo
circles, so I won't argue that point.)

>Yes I know that the full frame B models can be masked  down, but if you
are going to do that why >waste the extra film?

By your definition of "waste", practically every stereo mount in
existence "wastes" film, because they all mask part of the image to set
the window.

I find it very helpful to have "extra" image area to work with,
especially when some element that I didn't catch in the viewfinder
creeps in at the edges.  The wider the original image area was, the less
you have to sacrifice when you are forced to crop due to window
violation or whatever.  Worst case, I have mounted a full-frame image in
a 5-perf mount and "saved" an otherwise-ruined (compositionally poor
grab shot) image.  I don't call that wasting film; that's saving film!

Personally I find wider frames more compelling and "immersive" than
their narrower counterparts, which I find to be kind of like looking
through a tunnel at your subject.  If you've ever seen panoramic stereo
(it was shown at NSA in Bellevue) you'd never want to go back to 5-perf!

     -Greg W. (gjw@xxxxxxxxxx)



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