P3D Abram Klooswyk on stereoscope adjustments

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

Abram Klooswyk, thank you for a very interesting posting on stereoscope
adjustments and related concepts.  I have been enjoying your well-
written articles in (mostly older) issues of "Stereoscopy".

I have expressed similar ideas in my Realist red button viewer book.
"Using the Viewer" was first written 5 years ago and it is reproduced 
almost without change in this second (just released) edition. I tried 
to promote the idea that there is such a thing as a universal setting 
for focusing and interocular adjustment and that the viewer should not 
be adjusted by inexperienced users: "Asking an inexperienced individual 
to adjust the viewer is like asking for trouble."

In the book I also express surprise that the subject of using the viewer
is not discussed in popular books.  Stereoscopes are taken for granted.
Simple devices.  Do I need instructions?  No way!  The advice is usually 
given to adjust the viewer so that "the best position is found".  I have 
seen people pass the viewer saying "adjust the focusing and interocular
where it seems best for you" and have seen viewers totally screwed up
by such (mis)adjustments and wondered how is it possible a person to be
seeing stereo like that (maybe they don't.... for sure they cannot be
enjoying it).

So in my book I take the time to explain how to set the interocular 
at the infinity spacing of the stereo image and how to focus the viewer 
so that the eyes are relaxed at infinity, just as you suggested.

You wrote:

>    If David Brewster had fixed a standard separation for the optical
>    axes of his stereoscope (and consequently for the views) it would 
>    have saved us a lot of trouble, but Brewster was the first who made
>    the error to adjust the lenses to the interpupillary. 

I'd say we are lucky that he did not introduce a vertical adjustment!!!
Imagine inexperienced users trying to adjust the lenses vertically???

Which brings me to the subject discussed earlier ("beaten to death",
according to some people) regarding projector adjustments.  While no
one expects a stereoscope to have a vertical adjustment, everyone expects
the projector to have such adjustment and some people believe that
this adjustment should be "fine-tuned" from slide to slide.  Same for the
interaxial adjustment of the projector.  I tried to explain that these
adjustments are there to accommodate the first slide.  After the first
slide has been adjusted (and assuming that all slides are mounted in
standard stereo mounts and with some *minimum* degree of competence)
then no further adjustment is necessary, with the exception of focusing
to take care of mounts of different thickness.  

But, "No Sir!".  This is dictatorship.  People today want democracy in
stereo.  They want the freedom to screw up the projector by misadjusting 
it to eliminate ghosting and sloppy mounting, screwing everyone's eyes 
in the process.  Well, here is what I am going to do for these people:  

I will introduce a new stereo viewer with a control that allows you to 
move the lenses vertically, to satisfy those who cannot mount well, plus 
I will ask Bob Brackett to introduce a few more adjustments in his new 
projectors (how about a "rotation adjustment" or a "keystone distortion
adjustment"? - there must be a reason that God gave us 10 fingers but
only 2 eyes.)  Plus, supply the projectors with a dozen or so flexible
cords for the entire club to join the fun.  Here is a chance for all
members to actively participate in the meetings.  Every member will be 
assigned a separate control and "let the party begin!"

With deep regards,

George Themelis


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End of PHOTO-3D Digest 2878
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