[photo-3d] Halogen Bulbs and other projection issues...

["Dr. George A. Themelis" <drt-3d@xxxxxxx>]

David H. et al,.

I am very interested in every aspect of stereo projection,
from polarizing materials to screens and projection light
bulbs.  I was waiting to hear from people who have 
actually used the halogen bulbs and compared them to
regular tungsten bulbs but I guess no one wants to
step forward.

There have been several discussions in the past in
photo-3d on this topic.  I think I have saved the most
important of them.  My personal experience is this:
I have compared the 500W and 750W bulbs both
regular Tungsten and Halogen in a 116 and a 716 TDC
projectors.  That's 4 different bulbs in 2 projectors,
a total of 8 combinations.  I have measured the light
output with a digital light meter.  I do not have the
exact numbers on hand but I remember the conclusions:

- The 750W bulbs give slightly brighter images than 
the 500W.  The difference is really small and this
made me wonder if it is worth using the 750W bulbs
in my TDC 116 (which is what I have now, mainly
because I could not find any 500W bulbs)

- The Halogen bulbs result in dimmer images.  Because
of this observation, I do not use halogen bulbs in my
TDC 116.

I hope to put all this information in a practical handbook
on stereo projection.  This will cover the basic principles
of stereo projection, cover the TDC Projectors in great
length and give practical tips on optimizing the stereo
projection process.  Here are some areas I would like
to investigate further:

- Voltage and power distribution:  I have measured the
actual power applied to the projection bulbs (by
measuring the voltage and current) and it is much lower
than the ratings of 500W and 750W.  I would like to 
know why is this happening.

- Lens/mirror optimization.  Has anyone checked the
condition of the mirrors in the back of a TDC projector?
Are they clean?  Is the silver coating in good shape?  Are
they aligned?  (They can be adjusted).  I mentioned earlier
that my TDC 116 projector is noticeably brighter than
other TDCs that have gone through my hands.  Since
nothing else can move or cleaned or adjusted in the
optical system, maybe these mirrors are the answer.

Common problems/issues with the TDC projectors that
need to be addressed:

- Condition of the fan motor in the 116.  Many times this
motor is slow to start.  Is this a problem?  Can it be
fixed?  Do you need to take it apart? (I can show you
how).  How about the oiling that is recommended.  Where
on earth are the oiling holes?

- Condition of the heat absorbing filters (mainly in the
716).  I have done a lot of work in this area, measuring
the temperature at the film gate and relating this to the
condition of the HA filters.  To check right away if you
have a problem, do this simple test:  Take the black
part of an RBT mount and put it right in front of the
lenses.  If it gets soft (will start deforming), then you 
have a problem!  Where to find replacement HA filters?

- Condition of metal lens holder (both 116 and 716)
Many times this thin piece of metal that holds the lenses
is deformed.  Is this a problem?  How can it be fixed?

Other optimization/modification issues:

- Enlarge 716 carrier for 7 sprockets viewing.  I'll show
you how to do it.  Can this be done for the Selectron
carrier too?

- Rewire the 116 to have the fan on while the lamps
are off.  Is this even recommended?

Other issues/questions:

- What different slide carriers are available and for
which projector?

- What different lenses are available for these
projectors?  Could you adapt a different pair of
lenses?

- How to check the polarizing filters in the projector?
How often need to be changed?  What is the best
polarizing material to use?

- What is the best screen material available?  What
types/sizes of screens are available?  How to make
your own screen.

- What bulbs are the best?  Could you use low
voltage halogen bulbs?

Some general projection issues:

- How to mount for projection.
- How to adjust the projector.
- Should the projection be adjusted during a show?
- How to place the audience in the room.
- Small vs. large screen projection.
- How to put a projection show together.

These are some of the issues I would like to cover.
What I need is time.  Even if I start tomorrow (so to
speak), I will not have time to complete this "practical
handbook" for the NSA convention in July.  So I think
I will take my time and complete this next year.
 
I am sure I will be asking for help from the many
knowledgeable people in this list!

George Themelis

>As similar as these sound, there may be pronounced differences 
>in the actual performance in a projector.  As Tom Hubin as 
>demonstrated, minor (seemingly insignificant, and often unpublished) 
>differences in lamp and projector construction can give radically 
>different amounts of light on the screen.  (It has been demonstrated 
>that a 750w lamp can actually put LESS light on the screen than 
>a 500w lamp...differences in the filament grid area meant that 
>the condensors could not focus all of the light into the lens.)

and:

> Thanks so much Mike, the info you give us is great,(more than I was 
> hopping for) I think people who are selling those Halogen Bulbs on the
> net sometimes post messages here, but likely dont want to share the 
> info, thanks again for your time & effort, David H. 



 

Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/