P3D Re: Hypo, Hyper, Ortho

[roberts@xxxxxxxxxxxxxxxxx (John W Roberts)]

>Date: Sun, 7 Dec 1997 02:45:56 -0700
>From: Larry Berlin <lberlin@xxxxxxxxx>
>Subject: P3D Re: Hypo, Hyper, Ortho

>>From: John W Roberts  writes:
>>(I would even venture so far as to speculate that to be truly "ortho",
>>a 3D photo should be mounted to *infinity* (if it contains objects that are
>>at "infinity"), rather than to *the stereo window*. I'm aware that mounting 
>>to infinity can cause serious problems for projection.)

>*****  Do you mean that a mounted pair of prints would appear to have the
>image projecting completely above or in front of the prints?

No, I mean mount it so that objects which are at "infinity" in the photo
(e.g. the moon in the background of a landscape) also appear to be at infinity
(viewed with the eyes parallel) when seen in a viewer. You would then let
the objects in the foreground fall where they may, instead of the much more
usual method of trying to mount the photos so the nearest object is at the 
stereo window (and letting the background fall where it may). The angular
convergence of the eyes to converge on any particular object in the field
of view would then be much closer to what it would be in "real life" than it
would for a stereo-window mounted photo for which the real and virtual
infinities didn't happen to match up.

As noted before, mounting to infinity can cause significant viewing problems
if the image is *projected* onto a large screen, causing the disparity of
the projected image to become greater than the normal human interocular.
Also, I don't believe that stereo photos should always have as much
orthoness (be as orthoful?) as possible - but for those who really want
ortho, I expect that mounting to infinity would be useful.

John R

P.S. I would prefer to call the procedure I described "mounting to infinity"
(or perhaps "ortho mounting"?), and the procedure you described "setting the 
stereo window to infinity".

P.P.S. "Mounting to infinity" should be possible even if the original scene
doesn't happen to contain infinity - but I doubt it would be easy, without
a dedicated stereo camera and built-in masks. Perhaps a Realist photo with
a standard mount and *no* lateral adjustment of the film chips
approximates this?


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