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Old 10-02-2005, 12:33 PM   #1
higher
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Default The Aspects of Lighting, An Extremely Interesting Read!

Taken From: http://www.geocities.com/ptimlin/lighting1.html

Compiled by Richard Sexton.

Full article availiable from http://www.geocities.com/ptimlin/lighting1.html

Here's a sneak peak at it.

Quote:
o Plant Growth Lights

Epitomized by the Sylvania Gro-Lux (tm) tube, plant growth lights are, unlike all other fluorescent tubes, meant solely for promoting plant growth; you won't find these illuminating somebody's home or office - with one exception. Where I work, a receptionist thought it would be nice to have pink lighting in the lobby and ordered and had installed some plant growth tubes. You do get used to it, but they are most disconcerting when initially encountered.

GE's version of this tube is called "Gro-N-Sho", other plant growth tubes that are available are these tubes relabelled for specialty pet/aquarium companies. Gro-Lux type tubes have an output spectra with two large spikes. One in the blue, and one in the red portion of the spectra. There is almost no light emitted in any other portion of the spectra and as such, they cast an eerie purplish glow, and do not appear very bright. The spikes in the red and blue occur quite abruptly and are quite steep. This spectra was chosen as it matched the absorption of visible light by chlorophyll in a test tube. In the 50's a study was conducted on various lighting types and phosphor formulation on plant growth, the results of which were published in the book "Lighting for Optimal Plant Growth" (Kent State Press) The phosphor formulation of Gro-Lux type tubes was improved upon. Instead of two steep abrupt spikes in the red and blue, there are two slow rising large "bumps"; the peaks in the red and blue were not as high, nor did they rise as sharply. Instead of concentrating all the energy in these two narrow energy bands, the output was tuned to a wider output spectra still however, centered around red and blue. It became commercially available from Sylvania as Gro-Lux Wide Spectrum; GE named theirs Gro-N-Sho Wide Spectrum. These are more pinkish than purple and are indeed what is in the lobby of the building where I work.

Incidentally, you could never get away with regular Gro-Lux (as opposed to Gro-Lux wide spectrum) tubes in a lobby; they look dark, don't illuminate well and are a very deep purple. The Wide spectrum plant lights are brighter and don't look like a 60's psychedelic poster shop when used to illuminate a room like a regular Gro-Lux would.

Philips makes a plant light they named "Agro-Lite", which is a minor variant of the wide spectrum Gro-Lux. They commissioned a study at a major American university comparing their Agro-Lite to wide spectrum plant lights. The Philips tube resulted in 2 - 10% greater growth in a variety of terrestrial food crops when compared to other wide spectrum plant lights. Since these tubes are quite commonly used for (non aquatic) houseplants they are reasonably common in hardware stores or nurseries, although what typically happens is a store will only sell one vendors fluorescent tubes. Even worse, they don't recognize the difference between plant lights and wide spectrum plant lights with the result being you will usually find plant lights or wide spectrum plant lights from one manufacturer in a store. Wide spectrum tubes are reasonably inexpensive, although regular Gro-Lux type tubes tend to be a bit more expensive still - the chemical that makes up the phosphor which produces red is the expensive part. In a pet shop these can be between $10 and $20. From a lighting supplier a Gro-Lux tube is about $9 while a wide spectrum tube is about $7.
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Old 11-02-2005, 03:19 PM   #2
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A point of note is that this article is extremely old, both pricing , availability and quality/efficiency of lighting technology had changed much over the decade....E.g the eballast, T5 , cheap MH, etc.

However the explanation on various lighting properties are fundamentally the same, e.g lumens, color temp, etc. So it best for newcomers to focus on reading this areas within the article.
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