P3D Reply to Larry's critique of the red button

["Dr. George A. Themelis" <DrT-3d@xxxxxxxxxxxxxxxxxxxxxxxxxxx>]

Sorry folks but I am getting a bit tired listening Larry Berlin 
criticize my beloved Stereo Realist red button viewer...

>What was worse
>was that being able to see as far as those edges, allowed me to sense the
>distortion created by the optics themselves. The entire view in a RED button
>is presented as if it's painted on the inside of a bowl. 

Sorry, I don't get it.  Are you talking about pincushion or barrel 
distortion (both two dimensional) or something else?  If you view a 
perfectly flat picture, does it look distorted in two dimensions or 
three dimensions?  Your "bowl" example indicates a distortion in the 
3-dimensional space.  There is no question that there is a bit (just a 
slight, hardly noticed) pincushion distortion in these lenses.  But if 
the distortion is the *same* for both lenses then it should only by 
seen in 2D and not 3D space.  

It is mainly by observing the FRAME (the perfectly straight and square 
frame of an RBT or aluminum mount) that this distortion can be noticed.  
This could not be possibly observed in a three-dimensional image!!!

> With full frames,
>you can definitely see it and trace the entire bowl surface with your eyes.

Exactly how many times have you used a red button viewer?  How many 
different viewers?  (YES, there are differences from viewers to viewers 
as the quality of the lenses is not the same in all of them and possibly 
the supplier has been changed a couple of times - also, I have seen 
viewers with lenses reversed - talking about distortion!!!) 

Who modified it/them for full-frame?  I have worked over a hundred red 
button and other viewers.  The magnitude of this distortion is minimal 
and you are blowing it out of proportion.

>However, that distortion is significant enough that I
>definitely don't prefer RED button viewers, though they are fun and 
>useful in the absence of something better.

They are "fun"?  This "don't prefer" RED button viewers sounds like 
the result of some experimentation and testing.  Exactly how many 
different STEREO SLIDE viewers have you tested and how?  Do you even 
shoot slides?  Have you ever shot a roll of slide film???

>Take particular notice of the triangulation/depth effect.

What exactly is the "triangulation/depth effect" that you ask us
to notice?

>I didn't say I don't like red button viewers, I pointed out their
>characteristic distortion, which is far more distortion than I'm used to
>seeing in most of the images I work with. When it comes to viewers, I'm 
>most happy with the foldable viewer from RBT which I bought while in 
>Bellevue at NSA.

Now, give me a break!!!  You prefer a cardboard viewer with plastic 
simple lenses to the red button?   A $10 cardboard viewer with plastic 
lenses that you have to squeeze to focus (and work hard to bring both 
lenses in focus and parallel to your image) to an all bakelite viewer 
with metal rack and pinion focusing, interocular adjustment, internal
illumination and achromatic lenses?  

And you don't see any distortion in the plastic lenses of this $10 
viewer?  How about chromatic aberration?  Do you see any of that?  
Don't you see the blue-colored edges?  Doesn't that bother you?  You 
have been hypersensitized to some minimal distortion and close your 
eyes to loads of false color?

Better slow down in this red button critique Larry and concentrate 
in something that you really know like computers, stereograms, etc.

WITH ALL DUE RESPECT --  George Themelis


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