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Re: [APD] 10,000K CF

The energies directly corelate with wavelength. Plants care somewhat, prefering red and blue more than green.

Bulbs what diff color temps will have diff mixes of phosphors and can have diff efficiencies for light output relative to energy input.  However, one would be hard pressed to find a general corelation  between bulbs of diff color temps and efficiency.

The infra red photons are the least useful for growing purposes -- unless your plants really need the heat, which is not usaully the case. The intitial output in a fluorescent lamp is of a large quantity of UV photons. It's these UV photons striking the phosphors that knock some of the electrons up a shell, from which unstable state the electrons collapse back to the normal "orbit", releasing lower energy photons in the process. A lot of factors can be involved in the efficiency of this process. It's not just techonological diffs, if by that you mean the fundamental design type. Bulbs of the same basic design can vary in terms of the electrical resitance of the filaments, the quality of the filament coating, the quality of the phosphor coating, the gas, etc. Even within the same run on the same line, individual bulbs will vary somewhat -- and certianly there are variances from brand to brand. 

As a rule of thumb, one can consider that a bulb with almost no red or green output will have a high color temp, although that says nothing about the overall efficiency or level of light output. 


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----- Original Message ----
From: Jerry Baker <jerry at bakerweb_biz>
To: aquatic plants digest <aquatic-plants at actwin_com>
Sent: Wednesday, January 17, 2007 3:19:45 PM
Subject: Re: [APD] 10,000K CF

S. Hieber wrote:
> There's not direct correlation between color temperature and the amount of light output. Diff bulbs can have higher or lower otuput than others regardless of color temp.

Seems like barring any major technological differences, all bulbs should 
output roughly equal energies for a given wattage. Since photons are 
discrete quanta the actual number of photons emitted from a particular 
bulb can vary depending on its color (less higher energy photons - like 
blue and more lower energy photons - like red), but the overall energy 
output should be the same. Which brings to mind a question: Do plants 
care about photon quantities, or energies? Given that PPFD is used to 
measure photosynthetic potential, I assume it is the number of photons 
that matter. If that is the case, it seems like the lower the color 
temperature, the more effective it is for photosynthesis (generating 
more photons per watt).

"He who throws dirt is sure to lose ground."

Jerry Baker
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