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Re: [APD] light and the w/gal rule

The wpg recs are generally only offered for high flos and
MHs, which have roughly the same efficiency.

Wpg is a hand wave. It's a simple rough and ready way to
hit a target that's a mile wide. You don't need a
telescopic sight to hit a barn door. They wouldn't hurt but
they aren't readily available to most folks, who luckily
don't really need them.

It's not that a person can't find out a lot more info than
is readily available and then with some work, apply it to
what bulbs they put on their aquarium. But in the long run
I think a person would be hard pressed to show that their
tanks grew better than others' and the reason was the bulbs
that are x% stronger than those the others use.

How much light do you need on your porch? About 15 watts
fluorescent or about 40-60 incandescent.  Could a finer
prescription be develooped? Sure. Would we have better
porches? Generally not, imo.



--- urville <urville at peoplepc_com> wrote:

> thats what my other post was about.  watts is just not
> the way to go. 
> not all watts are equal is what i'm saying. bulb
> effciency is a big part 
> of it and as wright was pointing out to me that includes
> wasted light in 
> the infrared and non useable uv spectrums. the numbers
> all around just 
> arent for our use and i think till this point there wasnt
> a need for 
> them, unless the exsist in some science journal
> somewhere.
> Jerry Baker wrote:
> >S. Hieber wrote:
> >  
> >
> >>Well, if you want to go whole hog, use Pearson's R to
> do a
> >>partial regression on all the relevent factors, and
> don't
> >>forget to take into account the spectral shift that
> occurs
> >>with age and variations that occur coming off the
> >>production line, etc. When you're all done, most folks
> will
> >>find that they wpg still works well, is close at hand
> and
> >>convenient, and works as anything else. It's not like
> there
> >>is some critical value of light that has to be obtained
> or
> >>else plants won't grow well. 
> >>    
> >>
> >
> >There is such a value, but it's probably different for
> individual plant 
> >species and aquarium conditions.
> >
> >One neat thing about regression analysis is that it
> doesn't matter *why* 
> >something is correlated, it just is or isn't. I can
> explain 96% of the 
> >PAR output using lumen data alone, and I will be within
> 3.5 PAR of the 
> >true PAR value 89% of the time. That's pretty good to
> me. It doesn't 
> >really motivate me to go find the source of that other
> 4%.
> >
> >Your suggestion gave me an idea. Since lumens are based
> upon almost the 
> >same spectrum of light that PAR is, but uses a weighted
> curve of 
> >perceived brightness as seen by the human eye, I
> wondered if lumens and 
> >watts taken together would make a more accurate
> predictor of PAR than 
> >lumens alone. Thank you for the idea. I now have a
> logarithmic equation 
> >with an r-squared of 0.98!!! Here's the equation:
> >
> >PAR = 0.13 x sqrt(lumens x watts)
> >
> >So, for an example let's use an AH Supply 55W bulb. We
> know it's 55 
> >watts and has about 4700 lumens. That comes out to a PAR
> of 66. Who 
> >knows how true this is?
> >
> >  
> >
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