[tech-3d] Re: Stereo Base Calc. with $20.. Handheld

["Allan Griffin" <agriffin@xxxxxxxxxx>]

Reference posting by Mike Davis and further discussion on the tech-3d List
ref his recommended calculator and calculation formula:

Hi Mike and All,

Mike has cleared up some points that were not clear to me in his piece.
Thanks Mike.  Mike says that his advices about calculating the stereo base
are entirely irrelevant if you can't vary the separation.  It seems to
follow then that those of us who use standard stereo cameras, including
custom RBT and the like for work in the mid-range, are not included in the
group to which the posting was directed.  Even in the field of twin-cameras
used for "wide-base" work, where the stereo base can be set according to any
value or formula one wishes, I find that the question of MORE or LESS stereo
"bite" is quite subjective.

Steve Spicer (a good friend of John Bercovitz and myself - and whose website
you quote) has expressed the opinion on several occasions that my hyper
stereos are more to his taste when I use LESS relative separation (flatter).
However, Boris Starosta says today that he finds that my stuff somewhat on
the FLAT side (it appears that he would prefer MORE relative separation or
stereo bite).  Since I am not the one proposing the theory in question, I
don't feel moved to make any of my stereo pairs more available on the web
than are at present available.

About the only other observation I feel like throwing into the ring is my
belief that, in the mid-field or central half or so of the bell-curve,
stereo is more appealing when the apparent scale approximates life as we
know it.  It is for this reason, I believe, that the use of a base close to
that of our natural eye separation, produces the best psychological response
across the board.  Standard stereo cameras with no variable base handle this
problem very well indeed.  Most people who leap into the twin camera arena
where the minimum base is usually over twice that of the human being,
produce stereos featuring "little" people until they learn that the distance
to the "near" point needs to be considerably increased unless an appropriate
increase in the local length of the lenses used is made (usually to 135mm).

I apologise to Mike for even suggesting that I would like to see sample
stereo pairs produced with one or more of the cameras, rigs or other that he
or John Bercovitz would use when applying the theories espoused in his piece
which he says is based on the premiss that you have an infinitely variable
stereo base available to you in the real world.  If not, I think he is
saying:  "This is not for you".

In conclusion, can someone on List try and tell me in layman's language
whether calculations made with the unit Mike recommends are for actual use
and not simply a theoretical exercise?  If so, how and on what kind of
camera gear is the infinitely variable base obtained over the full range
from very close to very far?

Allan







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