P3D Viewers, features & prices

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

Mark Bennett just got a Stereo Graphic Viewer and asks:

>I noticed that while all the interocular adjustments and focusing works
>great, the vertical edges of the slides seem to bow where as the cheap
>chinese 3-D viewer doesn't.

This is called "distortion"  Various lenses show this to various degrees.
Single element lenses show it more than double element lenses.  Also, you
might notice the chromatic aberration, i.e. blue and orange fringes around
the edges of objects.

I am working on a book on stereo slide viewers... Basically a viewer has
three parts:

- Optical (lenses)
- Mechanical (focusing & interocular adjustments)
- Electrical (illumination)

Optical:  Inexpensive viewers have single element lenses.  I recommend
achromatic lenses that minimize distortion and chromatic aberration.
Most better viewers have achromatic lenses, which is about as good as
it gets in slide stereo viewers.

Mechanical: Focusing is a must.  Interocular is useful if the lenses
are small.  Good viewers not only offer these adjustments but also
have solid & abuse resistant mechanisms like metal rack and pinions,
etc.

Electrical: I would be nice if the viewer has internal illumination and
light that is bright, uniform (across the viewing area) and constant
(not flickering).  Control of light intensity can be desirable if
viewing in environments with different levels of ambient illumination.

With these clarifications I would like to classify viewers in these
groups:

- Very inexpensive (under $10).  Usually point-to-light, no controls,
single element lenses.  Good to start, or get someone started.  Good
to mail to friends with slides.  Examples:  Radex by Reel 3-D ($3.25)

- Inexpensive (under $75).  Internal illumination and focusing.
Usually single element lenses, no interocular.  Examples:  Brumberger,
Star-D, Kodaslide I, Life Like, Stereo Graphic, TDC (standard) etc.

- Good and (relatively) expensive ($100 to $200).  Internal illumination, 
focusing and interocular, achromatic lenses.  Examples:  Revere/Wollensak,
TDC (Deluxe), Realist red button/green button, Kodaslide II.  (Note:
Realist green button and Kodaslide II can accept AC bulbs and have
a rheostat for brightness control.  Other, battery operated viewers,
can be fitted with a power supply that will do the same)

- Sequential viewers (usually over $200).  Examples:  Airequipt, Stereo
50, Roto-Vuer, Realist sequential, etc. 

- Special viewers (have the credit card ready):  Hugo de Wijs, J. Van
Erker.  (Check Golden for these)

Steve Berezin is doing a good service bringing the Star-D back and
with a choice of lenses, including achromatic lenses.  We cannot
depend on the older viewers for a constant supply.  Those interested
in wedding stereo photography, etc., would like to have sources of
contemporary stereo viewers and Steve Berezin, Jon Golden and Alan Lewis
all are doing a great service bringing quality products at reasonable
prices.

George Themelis

PS.  Looking for a Realist red button modified to 8p?  
     Check my sell-3d ad! :-)


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