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Re: Potassium and CF Lighting

> Date: Fri, 12 Nov 1999 11:21:34 -0800
> From: "Dixon, Steven T. (Exchange)" <stdixon at ben_bechtel.com>
> Subject: Potassium and CF Lighting
snip... (the stuff on Potassium)
> Compact Fluorescent Lighting.  I'm perplexed by various claims regarding the
> light output of CF lighting.  Many of us (myself included) have reported
> good results with these lights.  The bulbs between 5000K and 6700K seem to
> work very well for planted aquariums.  We all notice/report how bright the
> lights seem and how our plants are pearling more and growing well.
> There are a number of reports, starting with the manufacturers
> (CustomSeaLife, for example), that CF light produce more light per watt than
> regular (NO) fluorescent bulbs, including more light than the new efficient
> T-8 bulbs.  Now I realize the term "lumen" includes an element of human
> perception.  That a light might seem "bright" to the eye and yet a bulb that
> seems less bright might actually have more output as measured in lumens,
> that perception of light may not correlate with the actual output of the
> bulb-referred to as PAR, if I recall.
> Am I right in recalling that PAR ratings would give us a rating which would
> better correlate with plants general ability to use light than lumens?

A little. Not a whole lot. Each plant can have a different action spectrum,
and PAR is a relatively flat-spectrum standard. Most plants would like more
red and a bit more blue, with less energy wasted in green. The magenta
result would make your tank look truly grody. PAR's flat spectrum is a nice
compromise between visibility and color, while being better at predicting
average plant response than lumens (which is heavily green biased).
> A few weeks ago Michael Rubin sent me a copy of a note from Erik Olson
> which, if I paraphrase correctly, essentially stated that CF lights are not
> in fact more efficient, that they do not put out more light per watt than
> normal fluorescent bulbs.  I do not recall if Erik was referring to lumen or
> PAR output.  One of Erik's points was that the technology of the two types
> of bulbs was more or less the same--however it is that these bulbs actually
> work.
> Just to make a stupid observation of my own, all seem to agree that the new
> T-8 bulbs are more efficient, which I take to mean that T-8 bulbs put out
> more light per watt (again, I'm not sure if we mean lumens or PAR when this
> is said) than the old T-12 bulbs.  So perhaps simply saying that all of
> these bulbs use the same technology doesn't really answer the efficiency
> question.
> Does anyone have a definitive answer to this question?  Do CF bulbs put out
> more light per watt (lumen or PAR) than regular fluorescent bulbs; than T-8
> bulbs?  Do we have data on this point?

Lumen or PAR output are spectrum dependent, so are determined mostly by the
phosphor(s) being used to convert the blue-uv mercury emissions to visible
light. The total light energy out per Watt is somewhat dependent on bore
diameter, so there is a marginal increase in output as the glass diameter
drops (phosphors, drive frequency and other factors being equal). The
technology is the same, but the output of T8s is brighter than T12s, and the
CFs are brighter still. The amounts are in the 10-20% range, as I recall, so
not totally decisive unless you are trying to cook your fish.

> Thanks for you views, and apologies for my use of the bandwidth today.

And thanks for educating me on potassium. No waste, IMHO. (^_^)


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