P3D Re: Enlarging Power Of Stereo Viewers

[fj834@xxxxxxxxxxxxxxxxxxxxx (Dr. George A. Themelis)]

>I recently saw an Iloca Stereo viewer for bid on Ebay. The description noted
>that this viewer was special because of it's 10x lenses. Does anyone know
>what the lens powers are for the Realists, Revere 22, or the Kodaslide
>viewers? Exactly how many times larger would a 10x make the slide image
>bigger, 10 times?

Al, my advice: Relax and enjoy what you have!  I have never actually
seen an Iloca stereo viewer but I have heard reports that were not
very favorable.

Most stereo slide viewers for the 41x101 format have lenses which are
20-25 mm in diameter and 44-50 mm in focal length.  The magnification
is directly related to focal length (FL):

M = 250mm/FL  (some people add 1: M = 250/FL + 1, I skip it)

John B has posted about lens magnification and written at least one
article (in one of Dalia's early magazines)

If you plug the typical focal length of 44-50 mm found in most viewers
(Realist, Kodaslide II, Revere, etc. have the shorter end 44 mm, 
Brumberger and most inexpensive single-element viewers are in the
longer end of this range, 50 mm), you get a range of 5x-6X magnification
for these viewers.

Now, for the Iloca to have 10X magnification, the FL of the lenses
must be close to 25 mm.  Ha, ha, ha!!!  That's a joke!  The shortest
lenses to have been used in these viewers are not shorter than 35 mm
FL.  The Gold button Realist viewer has 35 mm lenses and you can
hardly see the full 5p view,...can you imagine what will happen with
25 mm FL lenses?  Maybe for View-Master...

The 10x magnification of the Iloca viewer is definitely an exaggerated
number.  And, as I said, the reports I've heard were not very
favorable of the viewer.  I'd stick with the Red button, Revere,
Kodaslide II, TDC Deluxe instead... (and save some money I am sure!)

George Themelis