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I heard that there is strong evidence about....
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revengeishere
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Joined: 23 Jul 2003

PostPosted: 2003.08.20(Wed)17:37    Post subject: I heard that there is strong evidence about.... Reply with quote

spectrum v. intensity, that intensity is much more important than spectrum. I also heard that overpriced lighting companies just perpetuated the myth about spectrum. Does anybody know a site that talks about this? I've been searching with no luck.

thanks.
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ISquishWorms
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Joined: 06 Feb 2003

PostPosted: 2003.08.20(Wed)19:15    Post subject: Reply with quote

This article might be of interest to you there are also some others about lighting on this site.

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Steve Hampton
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Joined: 05 Feb 2003
Location: Jacksonville, FL

PostPosted: 2003.08.21(Thu)8:38    Post subject: Re: I heard that there is strong evidence about.... Reply with quote

revengeishere wrote:
spectrum v. intensity, that intensity is much more important than spectrum. I also heard that overpriced lighting companies just perpetuated the myth about spectrum.


Lighting can be a really complex issue. Comparing bulb performance is quite a bit simpler. It is also all but impossible to give many generalized answers or make generalized statements regarding lighting. However there are a few things that can be stated with a fair amount of certainty.

1) If you provide enough intensity then spectrum isn't as big of an issue for plant growth. Spectrum still has a big influence in the type of growth produced even under strong intensity so for many people it's still a major issue.

2) It is not a myth. Spectrum is a major issue in plant growth. However, for low light situations and for most of the commonly available plant species any bulb that is within the 4100K to 10000K color temperature range will have sufficient spectral output to grow plants. Note that K or Kelvin and Spectrum are two totally different issues. The K of a bulb is almost entirely a viewing preference issue. Meaning, how the color of the bulbs "looks" is the biggest issue regarding the K rating.

Why is spectrum important? Rather than refer you to a website I'll simply repost something that Tula posted several months back...it's better than anything else on the web.

Quoted from 2la's post:
Quote:
The light spectrum is measured in nanometers, corresponding to the wavelengths of emitted light. Recall from your physics studies, however, that light behaves both as waves and as discrete particles, or quanta. PAR is one measure of this quantum characteristic of light measured in microEinsteins per second per square meter, and it suggests that any quantum of light absorbed from light emitted at wavelengths between 400nm and 700nm is equal to any other quantum within the same range with respect to the amount of photosynthesis that takes place as a result of its absorption. Thus, a plant absorbing a quantum emitted at 670nm (in the red area of the spectrum) translates that energy into the same amount of carbohydrate production as it would if it absorbed a quantum of light emitted at a wavelength of 420nm (in the blue area of the spectrum) as it would if it absorbed a quantum of light emitted at a wavelength of 550nm (in the green area of the spectrum).

This might lead one to believe that plants utilize light in all areas of the visible spectrum (which closely corresponds with the wavelength range described above) equally, and it thus shouldn't matter what a bulb's spectrum looks like as long as it produces a good amount of PAR. However, plants do not utilize (I.e., absorb) all wavelengths of emitted light equally, and this is where PAS comes in. Plants have various chlorophylls, carotenoids, and phycobilins that increase their ability to utilize more than a few discrete points in the active spectrum. However, they still show strong preferences for certain wavelengths, being better equipped to absorb light emitted in these areas (blue and blue-green owing to carotenoids, green and yellow owing to the phycobilins, and blue and red owing to the chlorophylls--which comprise most of the plant). When you look at the combined spectral curves depicting which wavelengths are most absorbed by the various pigments, you'll see that blue is heavily favored along with red. Green is less favored, and yellow and orange least of all. This means that green plants are green because they don't absorb those wavelengths as efficiently as they do red and blue wavelengths.

[/quote]
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PharCyde
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Joined: 06 Feb 2003
Location: Queensland

PostPosted: 2003.08.23(Sat)5:47    Post subject: Reply with quote

Spectrum is mostly for humans anyway. If you just attached a tube that gives off red and blue light for the plants, your plants would look blackish and "unnatural". Your fish probably won't like it either, so a full spectrum tube or a tube with all the colours of the rainbow will make the tank look better from a human and fish point of view.

I've heard intensity is better than spectrum, and the lumens is more important than the wattage as well, as watts aren't the light.
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revengeishere
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Joined: 23 Jul 2003

PostPosted: 2003.08.23(Sat)15:39    Post subject: Reply with quote

yep, watt is just the measurement of how much energy the bulb is using...

also, I read that diana wlastad, the author of a very great book suggest using cool and a plant bulb is the best way to grow egeria densa, a bright loving plant.
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Skysong
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Joined: 07 Feb 2003
Location: MB, Canada

PostPosted: 2003.08.23(Sat)17:56    Post subject: Reply with quote

2la's explanation is a very good one.... Smile
This might make a good FAQ topic, mods.... Wink

Thanks for finally ending the debate between my friend and I over this. Smile
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