P3D Re: Springsteen's Nomenclature

[abram klooswyk <abram.klooswyk@xxxxxx>]

[The following was written before the terrible december 1999
black-out of P3d, it was bounced end Dec, I  re-post it now,
as Bruce seems waiting.
If you need the references, the official archives at:
www.calcite.rocky.edu/photo-3d/   might not have them yet,
but you can try:
www.pauck.de/archive/mailinglist/photo-3d/
which is Marco Pauck's "mirror" site and can be searched for
"nomenclature".
Some statements are a duplication of what I said before or
later - I also get a little lost in time - but omitting it would be
more confusing]
=======

More or less by the way I have commented on aspects of
parts 1, 2, 2 1/2, 3a and 3b of Bruce Springsteen's Stereo
Nomenclature (P3d 3623 3627 3631 3648, 30 Nov -
15 Dec 1999, I printed it all ), in the digests P3d 3656, 3657.
Now some more comments.

I like the type of reasoning, especially in the definitions,
and I also dislike "fuzzy ex post facto practicality, not the
stuff of fundamental principle".
But: "Zwei Seelen wohnen, ach! in meiner Brust" (Two souls are
living, alas! in my breast, Goethe's Faust).
So after some time of abstract reasoning and clarity of fundamental
principles, I mostly think: let's go back to business.

Bruce wrote:
>Av = Ar.  The effective Angles (angular position relative to
>each eye's axis of vision) of all points in each view, and
>thus of the entire view, must be the same as would be seen
>from the station point in recording.

This is a nice general condition. It is nice especially for those
who know all about stereobase, focal length of camera and
stereoscope, sitting distance from projection screen, mounting,
infinity points, stereowindow, and so on. I mean the experts.

But for those who just begin to understand some technical details
of stereophotography the level of abstraction might be too high.
In any case, it seems easier for a beginner to understand the
individual effects of the variations of base, focal length,
separations on slides, then to try to keep the "effective
Angles" correct. How would she do that?

If I understand it right, Bruce tries to define "orthostereo-
scopy" as a way of viewing, using the right angles, and being
independent of stereobase conditions.
This reminded me of the classical distinction between
"orthostereoscopic" and "tautomorphic" (See also P3d 3657).
The former has been defined to mean a space-image which
resembles the original closely, but may differ in size, so
a hyper or hypo also could be orthostereoscopic, like Bruce
suggests now.
(I had not discussed this distinction on the list before, because
it seemed a useless complication, but I should have known
that Bruce's philosophical research gave me no way out :-))

But the glossary definitions of the terms "orthostereoscopic"
and "tautomorphic" do *not* include the technical conditions
which should be fulfilled to achieve images which deserve
those names.
Also, the fact that these terms exist does not include a
technical or aesthetic verdict. The word "ortho" may suggest
something right, but that is too orthodox ...

Bruce: >>I can't accept that David Lee's scenic hypers, or Pat
Whitehouse's nature hypos, belong in a category with
deformations like stretch, squash, frustum, and skew<<

But why should an aesthetical judgement influence the description
of geometrical or perceptual facts? It cannot be denied that
scenic hypers do show a change of size. Whether you like
them or not is "not the stuff of fundamental principle".
As I see it, the main purpose of these theoretical terms is that
they faciliate some discussions, irrespective of esthetics.
Orthostereoscopic is just a descriptive term, not a
goal. Indeed some of the nicest stereopictures are
not "ortho" at all.

One set of conditions which often is mentioned as necessary
for "tautomorphic" includes a normal stereobase.
It seems that Bruce tries to eliminate this by replacing it by
a new condition (P3d 3648, 15 Dec 1999, after 5. TOO...)
Using the classical definitions this only means: substituting
tautomorphic by orthostereoscopic. I have no problem with
that, but I believe that many people (who never read to the end
of postings like this in the first place) will get confused by
different terms or redefining the old ones.

Bruce: >>I prefer a definition of orthostereo that pertains only
to viewing. To place any burden for ortho[stereo]scopy on the
taker of a picture, other than the necessary stereo recording
conditions I have laid out in Definition I, seems unfair to the
viewmaker and inconsistent with the rest of the classic
"deformations"<<
Here I must leave the game. My practical side refuses to go
along with a stereo theory in which the role of the picture
taker is diminished :-).

More fundamentally: I believe that in most forms of stereo
photography, or stereopicture making in general, the way of
viewing must be considered even before the picture is made.
(This is one of my objections against aspects of socalled MAOFD.)

I see stereoscopy as a *process* which begins with choosing
a camera (or other image producing hardware) and ends with
the stereo-illusion emerging in the mind of the viewing person.

Bruce:
>Our classic ortho-standard is half geometry and half
>ego - a strange brew!
Indeed, all stereoscopy is strange!

Usually it begins with recording of a pair of images on film,
which is governed by laws of geometrical optics, but it ends
with a private egocentric perceptual illusion which cannot be
shared directly.
This brew is a fact which no theory can change.

Abram Klooswyk