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DIY reflector

Just to clarify things, my company, an electric utility, gives customers
a rebate for certain 'measures' that help to reduce their electric
consumption.  One of these measures is the 'specular reflector', a piece
of metal with a mirror-like finish, specially formed to direct the light
downward (i.e., not just a flat sheet with a couple creases).  Another
measure is the T-8 lamp (and accompanying electronic ballast).  We have
no financial interest, whatsoever, in promoting one kind of measure over

The first point I think I should mention:
The rule of thumb we use that Bob Dixon referred to, backed up by
measurements (which I used to have when working at another utility), is
that a four lamp fixture (plain white enameled box) can be 'gutted' and
retrofitted with a specular reflector and 3 lamps to give roughly the
same lumen output at the work surface.

Now for some confusion:
In an office, one of the main ways the reflector maintains the lumen
level is by redirecting stray light down to the work surface, light that
would otherwise be lighting the walls, etc.  So, sitting at a desk under
the fixture, the report you're reading would look just as bright with
the reflector and 3 lamps, as it did with the original 4 lamps and white

Previously I had assumed that the reflector would similarly help an
aquarium.  From what I _now_ understand, without a reflector, some of
this stray light would reach the plants by being reflected off the
glass.  So although I still suspect the reflector would provide more
lumens to the bottom of the tank, I don't know if the rule of thumb is
quite the same for an aquarium as it is for an office.  My apologies to
Bob and anyone else to whom I previously wrote regarding reflectors.  My
previous assumptions appear to be at least partially wrong.  I am
familiar with reflectors, but unfortunately only as they apply to human
environments.  I'm still learning about how they work in an aquarium.

The second point is in regards to the white paint vs. polished metal
discussion.  I've heard a similar argument from a lighting consultant
about their 'reflectance' being almost the same, but haven't seen any
figures to back it up.  Another thing to consider which you may have
observed is that white surfaces reflect light in a diffuse manner.  That
is, the light striking the reflector at a given angle is reflected in
several directions.  On the other hand, a mirror reflects light at an
angle directly related to the angle at which the light strikes the
mirror.  That's why you can see yourself clearly in a mirror, but not on
a piece of white enameled metal.  Any physics/optics experts out there
will hopefully clarify or correct what I just wrote.  Some people also
believe that another reason reflectors can maintain lumen levels is that
rather than having the light bounce all around inside the fixture and
losing intensity before leaving the fixture, the mirrored surface sends
the light right out.  As for me, I have sample pieces of specular
reflector material inside of my retrofitted hood. 

Wade Shimoda

P.S.  I'm not sure if this is what Matthew is referring to, but there
are ballasts with a higher 'ballast factor' that provide a higher lumen
level from a given fluorescent lamp, at the cost of greater electric
consumption.  Ballast factors are applied directly to the lumen output
of the lamp, if I'm not mistaken.  E.g., 3000 lumen lamp x 1.2 ballast
factor = 3600 lumens.