T3D Re: stereo math

[michaelk@xxxxxxxxxxx (Michael Kersenbrock)]

> it? I understand that viewer viewing is more forgiving than projection
> but is there really a different specification? Would one that is mounted
> perfectly for projection also be perfect in a hand viewer and if not,
> why not?

Jay,

I think You answered your own question.  When one says "perfectly",
one actually means "within limits" because there is no perfection in
this world other than in integer math (one plus one is perfectly two,
but two apples aren't exactly twice as much apple as one apple because
apples aren't identical).

The spec for "perfect", IMO, is that spec where making things any 
technically better (making the apples more exactly identical) makes
no perceived difference in result.   One might say that two apples that
are within a gram of each other are "perfectly matched" in size, even though
they aren't.

In terms of mounting, some of the specs are indeed the same, but
different at the same time.  Let me explain.

One that is talked about quite a bit is providing mounting accuracy so
that the viewer's eyes don't have to diverge more than a very small
value.  This requirement is the same for both projection-mounting
and for viewer mounting, so "it's the same".  However, it's also very
different.  The spec is applied to the viewing environment.  In projection
the slide is tremendously magnified  while in a viewer the magnification is
MUCH less.  In other words, the "accuracy" required as measured *at the slide*
is less in the viewer case because it takes less accuracy to achieve the
same "actual" spec which is measured in the viewing environment (projection
vs. hand-viewing).

To more directly address your question, projection-perfect is indeed 
"more perfect" than viewer-perfect,  and  as such makes it a subset of 
that qualifying for viewer-perfect.  Neither case are PERFECT perfect.  
They just are better than the spec (diminishing return in results) level of 
technical perfection.

As John has mentioned, it's really easy to see this is the case by
doing it.  A slide that looks absolutely fine and beautiful in a viewer
can blow one's brains out when looked at in projection.  For that 
matter a "projection-perfect" mounted slide may cause problems if it is
then projected on a much larger screen than it was intended for.

As I understand things anyway (definitely NOT perfect!).  :-)

Mike K.


P.S. - Yes, I simplified my example(s), but I don't believe that
       doing so made any difference to the point(s) being made.
       So if you want to crucify me for leaving out those details,
       please do so gently.  :-)


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