P3D Re: boris starosta's site

[Larry Berlin <lberlin@xxxxxxxxx>]

>Date: Wed, 3 Dec 97 
>From: bercov@xxxxxxxxxxx (John Bercovitz) writes:
>.......................
>>Dr.T writes:
>> My advice to Boris is to go beyond "ortho" and explore ALL faces
>> of the stereo experience.
>
>I agree in the sense that hypos and hypers can be fun sometimes.
>In fact, it is difficult to do macros with much depth in them unless 
>you do them as a hypos.  Not to mention the potential vergence problems 
>when you project a correctly-windowed ortho macro.  Also, it is difficult 
>to see the depth in a really large scene without doing a hyper.  This 
>condition is exacerbated by lower-than-ideal resolution in 35 mm format 
>and very low resolution on the computer screen.

****  I agree with both you and Dr. T. However, I'll point out that for
Macros done at a distance of 12 inches or less from the lenses, the
resulting images wouldn't even have the same subject matter in them unless
you were technically set up to take a HYPO picture. If you aimed at the same
subject matter from the technically Ortho stereo base of the interocular
distance you would have to rotate the cameras and create other distortions
just to get the same subject matter. 

You know this, but it leads into a question, why pay all this attention to
the terms Hypo, Hyper, and Ortho at all? They are merely limited descriptive
terms of the geometry of a situation and have very little to do with getting
a good stereo image. It would be far more practical to use the term
convergence, referring to the angle between the subject and your two eyes or
the stereo camera lenses as the universal operational parameter. 

Consider that for ORTHO pictures with a stereo camera, the ideal subject
distance is around 7 to 15 feet. That represents a finite range of
convergence angle. That *identical range* of convergence angle is needed for
either a Macro, or Micro or a Hyper distant scene of mountains to appear
with satisfying depth relationships. Use of the word Hypo for the macros,
says nothing about the actual viewing angles. Use of the term Hyper for the
distant mountain shots says nothing about actual angles that might have been
used to capture the shots or the distance used to obtain the angle. Those
words only indicate which direction the viewpoints have departed from normal
interocular distance, and *nothing* more specific than that. This makes
these terms almost worthless as a guide to anything. Why are they used and
depended on so heavily in discussions?

In other words, Hypo and Hyper just happen to descriptively apply to Macros
for close ups  or wide based stereos of distant scenes. The term doesn't
indicate any specific amount of difference from Ortho, just that a
difference exists. Getting a good stereo image depends far more on achieving
a suitable convergence angle (enough but not too much) than it does on
staying near the normal interocular distance. The appropriate convergence
angle applies continuosly and equally to the entire scale from Electron
Scanning Microscopes to Telephotos of the Moon. It is a much more applicable
detail with real meaning.

>>(Dr. T says)
>> Some of my best images are of buildings. ......................
>> We have all seen the models that architects make to show as how
>> a future site will look like.  Hyperstereos will give you the same
>> effect.  So, what is wrong with that?
>
>I agree that hyper is the way to go accompanied by a caveat/explanation 
>for the newcomers that this is a hyper so they won't wonder why the 
>building looks like a model instead fo a full-sized building.
..................
>
>John B
>

****  So why is the shrinkage factor such an important factor that we have
to explicitly point it out? We look at ordinary photos all the time and
don't need an explanation that the images we are viewing aren't full size.
We don't see a photo of a person and suggest it looks like a doll. Why is
there such a reaction to a stereo photo of some large object which shows it
at a smaller scale? Maybe it's the unfamiliar realism involved? I don't
experience this reaction though I can observe the scale changes which seem
extremely normal. The intrinsic meaning is abundantly clear without an
explanation. It's all too similar to taking an airplane ride and upon
looking out the window and seeing the ground and buildings from above, one
comments on how they look like toys or models. Yet photos from the air or
space are now common and after flying a few times it seems as normal to see
shrinkage with distance applied from above as it does to viewing the
distance horizontally from the ground. 

However, having said all this, I agree it can be helpful for beginners to be
provided explanations for stereo phenomena with which they may be unfamiliar.

Larry Berlin

Email: lberlin@xxxxxxxxx
http://www.sonic.net/~lberlin/
http://3dzine.simplenet.com/


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End of PHOTO-3D Digest 2435
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