Re: Lumens per watt-a non-scientific observation

>So, it looks like the T-8s have it!

In terms of efficacy (lumens per watt), HOs and VHOs are as bad as
incandescents, which include metal halides.

>It also shows that watts per gallon or any other
>reference that uses watts can be misleading, and is probably bordering on
>useless (like the much misused and utterly useless 'candlepower'). Lumens
>should be a more accurate measurement, and obviously the depth of the tank
>is more significant than the capacity.

Yes, watts per gallon is only good as a general indicator.

Candlepower or lux is the best measure because it accounts for the amount
of light that falls on a particular surface. Measured at a leaf, it tells
you how much light is actually reaching the leaf.

The lumen rating is for ALL the light that a lamp generates, but not all of
it is aimed where you want or reaches the water (T12 tubes being thicker
can block more light than T8 tubes--another reason T8s are more
energy-efficient). In a tube or bulb, only the lumens shining unobstructed
into your tank get to the plants. Reflectors can help re-direct the other
rays but not all lumens will go where you want. So lumens are a kind of
gross measure compared to candlepower or lux.

Greg. Tong
San Francisco, CA, USA
gtong at sirius_com

"Every infinity is composed of only two halves."