Once a year I volunteer to light a concert at a local church whose
main set of fixtures consists of some old
Altman-style 6x22's (mounted from the balcony ceiling - lovely
access!). These fixtures originally used the
typical FEL 1kw lamps, but a couple years ago the church folks decided
to try to save some energy and
switched them all to HX600 lamps. Along with a noticeable drop in
light output, I also seem to have
a really hard time getting those lamps to focus properly in the
fixtures. No matter how much "bench"
focusing of the lamps I try to do (where of course by "bench" I mean
focusing from the top of a Genie lift)
I can never seem to get rid of a dead spot in the middle of the field
- just can't flatten it out.
I compared the mechanical specs of the two types of lamps, and even
held up two of them side by side
for a visual check, and it appears that the location of the filament
relative to the base is the same, so the
light origin should be at about the same place within the optics of
the fixture.
Anyone have any clues (or experience) with what the problem might be
here? Sure would appreciate any
help getting rid of those dead spots (there's so little light left
coming out to begin with, I can't afford to lose
any more due to poor focus!).
Thanks,
Howard
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