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Re: Watts and hogwash

IDMiamiBob at aol_com wrote:

> Wright writes:
> > The tank is not free space, and your lamps -- even MH -- are not point
> >  sources. Light that you manage to get coupled into the tank through the top
> >  surface stays inside, like a light pipe, until it encounters some
> >  absorbing/refecting surface.
> It has been my experience that even a tank with nothing in it  but water and
> gravel can be a significant light source for an entire room.  Light manages
> to come out of it all over the place.  The reflectors on most light
This is mostly scattered ligth. By the water itself (Rayleigh scattering),
by imperfections/dirt in the vertical glass surfaces, and by the gravel.
If you take a diffuse reading with a photometer of that ambient ligth 
created by the aquarium in the room, and compare it with a diffuse reading of 
the aquarium ligths as seen directly by the photometer, you'll get orders of
magnitude difference. This difference is what is effectively being kept inside
the "wave guide" and eventually transformed into heat. Try to cover the gravel
in this bare tank with a black cloth or something alike and see the difference
it makes.

> situations are not nearly as focusing as a spot light, or even a typical
> flashlight, where the bulb is buried way back inside a concave dish.
I agree 100%, this is IMO one of the two points where we should put all our 
emphasis in designing a good ligth fixture: good reflectors. The other point 
is of course the use of high ballast factor ballasts and efficient ligth bulbs.
> Bob Dixon

- Ivo Busko
  Baltimore, MD