# Re: light bulb and tannins

```
>At 03:48 AM 01/19/2001 -0500, zxcvbob (Bob) wrote:
> > > I have 2 questions.  One is about those twisty fluorescent bulbs that
> > > are said to have the brightness of a 75 watt buld but only use 20
> > > watts.  My question is when you are calculation the watts per gallon,
> > > which number do you use?  Are those bad bulbs to use?
> >
> >You use the "20 watts" number, but you should discount it considerably
> >(25 percent?) because the manufacturers' numbers are overly
> >optimistic, and to account for the energy wasted by the intregrated
> >ballasts.
>
>At 03:48 PM 01/19/2001 -0500, Richard R also writes:
> >Scott, they mean brightness 75watt of Incandescent light bulb while it uses
> >only 20watts. It's only to compare. So you use the 20watt number.
> >Bob, you don't have to discount anything. Number of Watts has nothing to do
> >with output of the light bulb.
> >It is like this : P = U x I ( P= V x I in Canada ), Power = Voltage x
> Current

At Sat, 20 Jan 2001 -0800 Daniel A. Segel wrote
Subject: Re: light bulb and tannins

>I don't understand this reasoning. When people suggest a certain # of
>watts/gallon they're making the recommendation based on brightness, not
>power consumption. So if these bulbs really do put out the same brightness
>as a 75-Watt bulb, why would you only consider them a 20-Watt bulb for
>overall lighting calculations?
>
>Daniel Segel

Sorry for misunderstanding. I thing the 'watt per galon' rule is based on
watts of fluorescent light (tubes not compact fl.). I know, it's very
inaccurate, but simple. Just like the 20w  compact fluorescent "has"
brightness of 75w Incandescent light bulb, not accurate, but people roughly
know what kind of brightness they are getting.
What is bright for your eyes is not necessarly bright for plants and vice
versa.
Here are some good articles:
http://retirees.uwaterloo.ca/%7Ejerry/orchids/light.html
http://www.thekrib.com/Lights/
http://www.geocities.com/CapeCanaveral/4742/aquaria.html#lights

Richard

```