P3D Re: The world is ortho after all...

[Larry Berlin <lberlin@xxxxxxxxx>]

>Date: Fri, 12 Dec 1997
>From:Dr. George A. Themelis writes:
>.....................
>>>>(various comments from others)
>>>>I like to keep orthostereoscopy
>>>>in mind without 'believing in it'.  One doesn't violate ortho for
>>>>an effect, it is violated because it is not inviolate.
>>>
>>>I cannot follow this... I violate ortho for an effect... it is called
>>"hyper"
>>
>>I meant, it's violated for good reasons, to enhance imaging, not as a
>>special effect.
>
>That's questionable.  I use it mainly as a special effect.  There are good
>uses of hyperstereo in science and engineering where someone is going to
>measure something and get some information from the pair, but my personal
>photography is for enjoyment not science.  I enjoy the hyper effect.  It is
>different and it is fun when done in moderation.  But I wouldn't say that
>it "enhances imaging"...
>

**** I use hyper frequently as enhancement rather than special effect,
though I use it for a special effect too. (isn't enhancement an effect?) I
seldom know precisely what base I am using. However distant scenes always
look better as Hypers... that's enhancement.

Due to a stack of unread digests, I've obviously missed most of this debate,
but here goes. Ortho is a reference point. Period. It defines the most ideal
geometric reltaionships for stereo images with scenes that are about 7 feet
to 15 feet from the camera and a stereo base exactly matching the average
interocular distance. It is NOT the stereo base that's really important here
other than as a starting point and reference point (our eye spacing). What
IS important is the relationship of that base to the distance of the center
of the scene. This favorable relationship, which is a ratio, can be used for
distant scenes to advantage, where they accidently become what is called
Hyper because of changes in only one factor, the base factor. 

To further complicate things, ORTHO is only valid upon viewing the resulting
images in some rigidly defined circumstance relative to the taking
equipment. Since that is relatively rare within the total range of stereo
image usage, it's primary value is as a scientific curiosity. Used as a
critical factor to rate stereo images or as a magic formula for taking
images, it falls a bit short. 

Those who use fixed base stereo cameras already know there are definite
limits to what will make a good picture relative to the camera. How sad that
some stereographers have been suckered into believing such limits actually
are part of the stereo hobby scene. It isn't true. Ortho is a guideline with
a message, not the target for every picture. Twin rigs are closer to an
ideal stereo camera for this reason, except that most cameras are too large
to provide access to a normal interocular spacing. Single cameras are ideal,
other than you can't use them for capturing objects in motion.

An ideal stereo camera would NOT be fixed base. It would freely adjust from
hypo to hyper according to the needs for each picture. That sort of
eliminates most film cameras since they are too big. Some newer ones are
small enough to come close. Only the concept of using digital imaging, which
can be done with relatively small sensors that can be freely placed wherever
needed approaches providing a promise of an ideal stereo camera. An ideal
stereo film camera would use two separate strips of film so the lenses can
be freely maneuvered as needed. 

I like the idea of understanding and using Ortho, but not the idea of
religiously pursuing Orthoness as a requirement in ones photo work. I guess
that makes me a heretic per several previous comments. The value of Ortho is
in describing ratios that work so well in narrow but familiar circumstances
and which are usable everywhere to help get good results that aren't Ortho.
That's a FREE-style way of using Ortho instead of the limit method where
your picture isn't valid unless it is Ortho per stereo base AND matching
viewing gear. Why put so much energy into a dead end? Most of the world does
NOT have a means of insuring an Ortho viewing experience. I'm not convinced
it's at all necessary. However, getting that ratio of base to distance right
seems to ALWAYS be a factor in good stereo images, regardless of any viewing
method or circumstance, Ortho or not.

I'll stick to the ortho church of harmonious convergence, thank you very
much...  ;-)

Larry Berlin

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


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End of PHOTO-3D Digest 2457
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