P3D Re: super bright viewers

[Steve Berezin <sbere@xxxxxxxxxxxxx>]

Mark Shields wrote:
> 
> Has anyone else done anything with viewers brighter than
> the by-now-normal halogen (thanks to Dr. T) type? It seems I
> saw a catalog listing of a bulb that was a lot brighter
> than the usual choice, with a somewhat facetious indication
> that this was the way to go for the adventuresome who
> wanted _really_ bright images.
> 
> Mark Shields

Before I put the halogen bulbs in the Star-D I did extensive work with
Xenon bulbs designed for caving helmets.  These were brighter than the
traditional screw based halogen, and also gave a very white light and
came in a very wide variety of voltages.  I modified a few Star-D's and
added battery saver outlets and added them to wall warts.  I was able to
get to very high brightness.  The problem was that most of the
reflectors in modern viewers do not have the ability to withstand the
heat generated by the bulbs very well (Not to mention the slides).  Heat
absorbing glass and things can be added but it was not practical for a
low priced commercially produced viewer. Although the heat produced was
low compared to the brightness, it was still more than the traditional
halogen bulb produces.

I made several other viewers based on the brighter Xenon bulb but felt I
needed to add a dimmer to allow people to diminish the light if they
were viewing slides in a dark room.  Although AC current would allow a
simple commercially available Rheostat to be used for a dimmer, DC
current required that I make a potentiometer, resister, transistor
combination that would be expensive and time-consuming to produce en
masse. I did however make a few for my own use which I was happy with. 
These were very useful for viewing some underexposed slides I made while
I was at Carlsbad Caverns two summers ago.  DC dimmers are commercially
available (generally used as instrument light dimmers on automobiles,
12V) but are priced too high to be practical.  Simply using a
potentiometer is insufficient for adequate dimming, it will either burn
out and have a very short lifetime or produce irritating graduations
(both non linear or linear).

I have also done some work with white light super bright LED's.  So far
this has worked well but even the white light ones have lenses and need
extra diffusion.

I found that graduations in brightness can also be achieved by moving
the reflector closer to the light source.  In comparing the LifeLike
viewer achromat (with a modified halogen bulb) and and the Star D
Achromat (with a halogen bulb), both of which we offer, the LifeLike is
noticeably brighter due to the proximity of the light to the reflector. 
I have found it to be about as bright as needed even in a bright room.

 
-- 
mailto:sbere@xxxxxxxxxxxxx
http://www.berezin.com/3d
Steve Berezin
Berezin Stereo Photography Products
21686 Abedul
Mission Viejo, CA 92691
USA