P3D Re: zoom lenses

["Greg Wageman" <gjw@xxxxxxxxxx>]

From: JNorman805@xxxxxxx <JNorman805@xxxxxxx>


>Gee, that's too bad.  I guess I've been wasting a lot of film with my
off-the-
>shelf Canon EOS 35-80 zoom lenses.  Not only should I toss the
home-made twin
>rig that I thought had served me so well, but I better get rid of all
those
>wasted pictures that have pleased me and others who have seen them so
much.
>And maybe I should tell my fellow APECers to dump my modest
contributions over
>the past year.  I guess what I am saying is that there's an awful lot
of
>"received wisdom" out there that may not withstand the
"proof-of-the-pudding
>test."  Some of my favorites:  You can't synch two cameras to the same
flash
>simply by splicing two remote shutter cables into the same button.  You
must
>use a bubble level or people looking at your pictures will get
headaches.

Please, Jim, can we lose the sarcasm?  It really doesn't bolster your
position any.

This list is full of testimonials about "cross-talk" (e.g. "hunting" of
autofocus, false triggering of one camera and not the other, etc.)
between cameras when splicing remote triggers, or cross-connecting
electronic shutter release circuits.  It is entirely dependent on the
circuitry of the cameras in question.  That it works in the case of one
model of camera is certainly not proof that no one else will ever have
problems with another model, which require diodes in the circuit to
prevent problems.

The "level-or-else" theory has been frequently debunked on this list.
Tilted stereos only offer, at most, a psychological challenge to some
people, that's all.  Personally I find a bubble level very helpful in
getting a perfectly horizontal horizon line.  They are even useful in
flat photography for this purpose, and in fact bubble levels are
available from B&H and other full-service 2D photography suppliers.

It is a fact that off-the-shelf lenses are not precision-matched.  The
David White company is well documented to have had a difficult (i.e.
expensive) time getting matched sets of lenses for the Realist (this is
ostensibly why they dropped Kodak Ektar lenses).  Since monocular camera
makers have absolutely no reason to ensure exact tolerances in their
lenses (they aren't advertising or selling them as matched pairs now,
are they?), there are numerous economic reasons for them NOT to maintain
such strict tolerances.  So the rule is "caveat emptor".

Maybe you DID just get lucky.  Again, there has been testimonial on this
list about people trying several different "identical" lenses before
they found a pair suitably closely matched for stereo.  Because you have
had good look is no reason to disparage good "heads-up" advice from
others.

Finally, the definition of "suitably closely matched" is entirely
subjective.

I've been doing a lot of experimentation with digital 3D since I got a
film scanner, and I've found that MY eyes, at least, will tolerate a
significant amount of rotation and/or vertical misalignment.  One
digital stereopair I've created has significant rotational error between
the two images because of scanning problems (specifically, scanning
Realist-format mounts in a 2x2 slide scanner without a jig), which
become really obvious if you look at the interlaced version without LCS
glasses.  You can see how features which should be vertically aligned,
are misaligned by tens of scan lines.  It fuses fine for me, but I can
feel a subtle "tweaking" of my eye muscles when I view it.  Would I want
to inflict this on others?  No.  Could some, maybe the majority of
people, fuse it?  Probably.  But since I'm aware there's a problem, I
can fix it, and I will before anyone else sees it.

I would hope that others would be as considerate.

     -Greg W. (gjw@xxxxxxxxxx)





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End of PHOTO-3D Digest 3037
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