P3D Re: " Orthostereoscopic"

[Larry Berlin <lberlin@xxxxxxxxx>]

> Date: Mon, 20 Dec 1999 
> From: Rehotshots@xxxxxxx
>.........
> In trying to figure out just what you mean by this term, I have come up with 
> this:
> 
> In order to get the stereo photograph to look undistorted, there are certain 
> mechanical processes that must be adhered to.  Well, maybe Larry doesn't want 
> his images to be undistorted.   Maybe distortion enhances the experience of 
> his images(?)  Larry?  Like a fisheye lens might, if you could change out the 
> lenses. ........

*****  I'm sure that by now, you've read Dr. T's series about many of
the basics. It should provide you with information to understand a lot
more. My experience with stereo provides lots of interest that is well
outside the narrow definition of Ortho, yet is not particularly
distorted in any way. Hence a strong resistance to language and
practices (including fixed base cameras) that provide the illusion that
that's the ONLY best way to do stereo.

> 
> "...includes the 'recording' requirement, and that it is often express in 
> terms of secondary necessities like focal length, matching and IPD..."  You 
> lost me there. 
> Will get it eventually though.  

*****  Bruce Springsteen's comments attempted to point out the inherent
limitations from using these secondary factors to define Ortho, instead
of the primary angular ones that exist in the stereo geometry. IPD
refers to Inter-pupillary distance, or more commonly, the distance
between your eyes. While fundamental to the stereo experience, one can
create and view hypers (taken from wider than IPD) or hypos (taken from
narrower than IPD) that are otherwise indistinguishable from an ortho
image. What is constant in this situation is the relative viewing angles
within each example image. In other words, one doesn't need to restrict
their fun to IPD situations at all! One does need to understand the
angles in Ortho geometry however if they want to get non-orthos to look
right.

If ortho were defined in terms of angles instead of absolute distances,
it would be more flexible. It's not. Plus the terms Hyper and Hypo ONLY
relate to variance from the critical factor in Ortho, the IPD. As viable
terms they would be more logical if they referred to distortions from
normal vision caused by the change of base distance, but in fact they
don't always exhibit distortion! It depends on getting the angles right!
The angles, though primary to the experience are basically ignored in
the definition of Ortho.

It's confusing having an entire system (both knowledge and technology)
built around secondary factors making translation to different
circumstances difficult and with terms like Hyper and Hypo and Pseudo to
scare people away from experimentation! ;-)

One literally has to break the Ortho -rules- to get a good stereo
picture in conditions that are outside the typical ortho arrangement.
One *should* only have to follow an angular measure guideline so that
pictures taken in or out of Ortho conditions remain easily viewable to
someone wanting to view them. It all boils down to the viewing
experience! Bruce's idea was to focus on viewing, and not have to worry
about the taking conditions. His reasoning for this was very good.

As Dr. T pointed out, there are lots of ways to view stereo, and some of
them are extremely dependent on particular devices.

As one who prefers freeviewing generally, I find that very few such
limits apply anymore. That is not to say that I don't appreciate the
experience of a great set of slides, with all factors properly accounted
for in a hand held viewer! 

Larry Berlin

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