Re: Projection lamps

[P3D Larry Berlin <lberlin@xxxxxxxxx>]

>Allan Woods writes:
> .... There seem to be so many different designs.  I was wondering
>how to get a "real life" comparison based on "performance."
>
>How do 12V, 24V, 120V lamps differ (other than they require different
>operating voltages and consequently, current flow) ?

************  The type of bulb is of greater effect than the voltage design.
Halogens for example are available in each of these voltages and would
provide a whiter, brighter light than ordinary filament lamps. Another
consideration is the power supply. Anything less than line voltage requires
the appropriate transformer which adds mass to the projector/system. Lower
voltages are considered safer to work with or around.

One could argue that since the ideal light is sunlight, which doesn't
alternate or flicker, the ideal projector system would be powered by Direct
Current voltage. A power supply could be designed for any voltage system
that delivers ripple free current to the projector lamp. There are safety
concerns with DC, but the light output would seem cleaner and could provide
a subtle but important benefit of reducing potential eye stress.

I know that the *experts* claim that we aren't really aware of light level
changes that are very rapid, but I certainly am aware of 60 Hz fluctuations
and I suspect the nervous system responds to high speed fluctuations even if
it's at a very subtle level. Battery operated viewers are flicker free
unless they have a bad connection in the switch.

>
>Why pick one over another?

*************   1. get one that works in a given projector  2. provides the
levels of light/color required by the projection geometry or desired by the
projectionist 3. longevity  4. cost

>
>If bare bulbs emit light in (almost) all directions, does a bulb
>with a built-in reflector emit twice as much light to one side
>than if it had no reflector?

*************  Potentially much more than double because you are
concentrating and redirecting light from many directions to a narrow region.

>Another frame of reference is: If you were going to make a projector
>from scratch, how would you choose a light source? (...other than
>cost, broad availability, transformer requirements, etc...)  ...or
>are those too many restrictions?

*************  I'd be tempted to start with halogens because of their
intense brightness and good color. It helps that they are far more readily
available than they used to be. It also depends on how far and large you
intend to project... You may want super lasers if you intend to write or
draw images projected on the moon ... Lunar anaglyphic line drawings?
(Where's my 3D medication ... ; -)

Larry Berlin

Email: lberlin@xxxxxxxxx
http://www.sonic.net/~lberlin/


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