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Xenon lighting
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aychamo
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Joined: 30 May 2004

PostPosted: 2004.06.14(Mon)17:41    Post subject: Xenon lighting Reply with quote

Hey guys!

I spent nearly an hour at the hardware store today trying to fight lighting alternatives to my 10 gallon tank's current lighting.

I saw they had a xenon fixture, which was made for under-cabinet lighting, and it would work on my tank with it's dimensions. The fixture had 3x18w xenon lights, and was about $35. The package mentioned that they were low temperature and did not have produce harmful UV rays.

Would xenon lighting work for growing plants? Or, more importantly, is the 3x18w equivelant to a 3x18 flouresccent?

Also, I saw small nice, small, 23w compact flourescent lights, but I couldn't anywhere in the store find the "housings" that you would mount the CF lights in. I did see a few lamps that had 13w CF lights in them, and it seemed like it would be easy to harvest the CF lighting fixture from them.

Also, I saw some nice shop lights that had really good reflective coating in the back of them, and either a 13w or a 26w CF bulb in them. It seems like I could modify the shop lights to fit nicely in my fixtures. My question here would be how does it work if say I have a lot of light, but it's over a small area. Err, like my tank is 20" across, and the "bulb" of these lights was only say 8 inches. I could lie them facing opposite directions, but there would be areas of the tank not covered directly overhead by light. Is this an issue? I could probably put a third to cover the entire area, that would give 3x13 = 39w.

Anyways, I'm just curious what you guys think about these ideas, and specifically the xenon lighting.
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mlody
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PostPosted: 2004.06.14(Mon)21:20    Post subject: Reply with quote

I would advise against xenon lighting in an aquarium just because it will save you a lot of money if you go with another form, such as CFs or regular ones. Lets compare the 2...

Xenon lights can produce the correct Kelvin rating to keep the plants you wish. Xenon lights produce about 3200 lumens (give or take 400) at about 32 watts. Xenon lights have a CRI (color refrence index) of about 95. Color refrence index is how well the light bulb produces the spectrum so our eyes do not notice a lack (or excess saturation) in certain colors. The life of the average Xenon lights is about 1,000 - 2,000 hours.

Flourescent bulbs can produce the correct light spectrums for aquatic life. Flourescent bulbs produce about 2,500 lumens ( give or take 400) at 40 watts or 1,700 lumens at 20 watts. The color refrence index of the average daylight flourescent is about 90. The average life span of a flourescent light is about 10,000 - 20,000 hours.

The huge diffrence is in the light of the 2 bulbs. The Xenon light is more expensive and the life span is much lower (10x lower). For this practical reason, I would not recommend the Xenon light. Other than that... Both the xenon and flourescent come in diffrent kelvin ratings. The only 2 advantages of Xenon are; the xenon light produces more light for the amount of physical space it takes up, and the second reason is that the CRI is better for the Xenon light. If you are looking for a lot of power in a small space, then the Metal Halide light does even a better job at it. If you are worried about the minimal diffrence in CRI, you can buy a higher quality flourescent to compensate. Either way you look at it the Xenon light is not worth the hastles.

CF lights and Regular flourescent bulbs are about the same, except the CF light can produce more light in a small space. With that in mind... people have squeezed enough bulbs on top of the tank with regular bulbs. So the finaly question which method will save you time and/or money (which ever is more valuable to you).

BTW: How big is your tank?
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2la
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PostPosted: 2004.06.14(Mon)22:49    Post subject: Reply with quote

mlody wrote:
Xenon lights can produce the correct Kelvin rating to keep the plants you wish.

Could you explain this statement in a bit more detail? IMO and IME, Kelvin rating tells you very little, if anything, about a bulb's plant-growing abilities. Kelvins, CRI are specs strictly for human eyes, not for plants' leaves.
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mlody
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PostPosted: 2004.06.15(Tue)1:35    Post subject: Reply with quote

Quote:
Could you explain this statement in a bit more detail? IMO and IME, Kelvin rating tells you very little, if anything, about a bulb's plant-growing abilities. Kelvins, CRI are specs strictly for human eyes, not for plants' leaves.


Unless I am mistaken, plants do require mostly a specfic spectrum that is made up of red (mostly), blue, and little bit of green. Kelvin rating probably tells you very little about the growing ability of the bulbs, but it is a nice refrence point. Idea I'm sure you will agree that a daylight bulb will grow healthier plants then a acintic bulb. These bulbs have diffrent kelvin values. I'm sure if you compare a 10K bulb with a 6,700K bulb you will notice very little diffrence, but if you compare a 6,700K bulb with a acintic blue bulb you will certainly notice the diffrence in growth; Another example is if you compare a 3,000K bulb with a 6,700K bulb. 3,000K bulbs will produce more tall plants with very few leaves at the bottom of their stems. If you take an acintic blue bulb and lay it side by side with a 6,700K bulb, the plant will bend towards the 6,700K bulb in an effort to obtain more red in the spectrum of light it receives. These bulbs have diffrent Kelvin values and this does effect the growth of a plant (in IME at least). CRIs are strictly for human eyes only, but if there is no diffrence between one type of bulb and another in it's plant growing ability then we can look at what has a better CRI. That way we can hit two birds with one stone and get the plant growing ability as well as the correct color refrence index.

The Kelvin rating of a give bulb is a specification of the spectrum of light emitted by a given light bulb which is similar to an object of a given temperature. This has nothing to do with the human eyes, correct Question
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aychamo
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PostPosted: 2004.06.15(Tue)8:17    Post subject: Reply with quote

Hey there!

I really appreciate the reply, and I'm probably going to end up getting CF bulbs. But let me make sure I understand correctly. Basically, you are saying that xenon is better than CF, but it just doesn't nearly as long and is more expensive?
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mlody
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PostPosted: 2004.06.15(Tue)10:42    Post subject: Reply with quote

Basically. I don't think that Xenon lighting is better then CF though. CF lighting is more versitile (meaning there are a lot more color temperatures to choose from as well as other things.) right now because of the high demand and practicality of these lights. You can't really say that one method is better then another here, because each has it's advantages and drawbacks. I would choose CF over Xenon anyday.
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2la
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PostPosted: 2004.06.15(Tue)13:31    Post subject: Reply with quote

mlody wrote:
Unless I am mistaken, plants do require mostly a specfic spectrum that is made up of red (mostly), blue, and little bit of green.

That is correct.

Quote:
Kelvin rating probably tells you very little about the growing ability of the bulbs, but it is a nice refrence point. Idea I'm sure you will agree that a daylight bulb will grow healthier plants then a acintic bulb. These bulbs have diffrent kelvin values.

Sure.

Quote:
I'm sure if you compare a 10K bulb with a 6,700K bulb you will notice very little diffrence...

I would disagree with that depending on the accuracy of the color temperature ratings...

Quote:
...but if you compare a 6,700K bulb with a acintic blue bulb you will certainly notice the diffrence in growth; Another example is if you compare a 3,000K bulb with a 6,700K bulb. 3,000K bulbs will produce more tall plants with very few leaves at the bottom of their stems. If you take an acintic blue bulb and lay it side by side with a 6,700K bulb, the plant will bend towards the 6,700K bulb in an effort to obtain more red in the spectrum of light it receives.

Let's use a real-life example. The Sylvania Grolux produces the following spectrum:



This gives you a color temperature rating of 3400K and a CRI of 89. The main difference between this bulb and many 'daylight' bulbs is the absence of a profound spike in the green area of the spectrum, which, while increasing color temperature into the 6000s and CRI into the 90s, adds little to the bulb's plant growing capabilities (assuming lumen output is roughly similar). All it really does is offer a different color rendition, and you can leave it up to your eyes to decide which looks better. Color temperature and CRI may help with that, but even that's not consistent.

Quote:
These bulbs have diffrent Kelvin values and this does effect the growth of a plant (in IME at least).

So how do you compare bulbs with the same Kelvin ratings? Note that in this comparison there are four bulbs rated at 5000K--each with very different spectra, CRIs ranging from 82 to 90, and even overall appearances that differ widely (yellowish versus pinkish versus creamy white)! Why is that?

Three reasons: 1) Color temperature ratings oftentimes seemed derived by manufacturers through black magic, 2) a single given color temperature can be derived in any number of ways owing to variances in the bulb's spectral output, and 3) color temperature gives you very little indication of a bulb's actual spectrum or lumen output, which are the more important factors in a bulb's ability to grow plants well.

For example, take a look at the following spectrum:



Many people have reported success using the bulb that gives off the spectrum above. Now, how different do the two spectra above appear? Based on that, what would you predict the color temperature to be? (Answer provided below...)

Quote:
CRIs are strictly for human eyes only, but if there is no diffrence between one type of bulb and another in it's plant growing ability then we can look at what has a better CRI.

Problem: If you can't use CRI (nor color temperature, for the reasons provided above), then how would you determine a bulb's plant-growing ability without first setting it in the fixture and turning it on?

Quote:
That way we can hit two birds with one stone and get the plant growing ability as well as the correct color refrence index.

The quest for a high CRI (actually color rendering index) is, IMO, way overrated. I've seen my tanks in pure sunlight before the lights come on, and the color rendition--while of course accurate--is rather bland: Greens are darker, but differences between shades of green are diminished and the reds and blues of my fish and/or plants are no longer as vibrant. I'll take the 67 CRI of my GE Aqua Rays and their ability to enhance the reds and blues of my tank anyday over a bulb that duplicates the previous effects. This, of course, is a matter of personal preference.

Quote:
The Kelvin rating of a give bulb is a specification of the spectrum of light emitted by a given light bulb which is similar to an object of a given temperature. This has nothing to do with the human eyes, correct Question

No and no, for the reasons cited above. You cannot accurately infer a spectrum from a given color temperature nor vice versa. And let's not forget that the designation of "actinic blue" is not a reference to color temperature but to the presence of a pronounced spectral output in the 400-500nm-wavelength range, usually centered around 420nm. What, for example, do you make of the Coralife Actinic Blue lamp, which is rated at 7100K?

The mystery spectrum belongs to the Hagen AquaGlo, which is rated at 18000K
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number6
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PostPosted: 2004.06.15(Tue)14:05    Post subject: Reply with quote

okay 2la, mlody, thank you for confusing the heck out of me! LOL
actually, I was wondering the same thing. I see recommendations to get a 6500 and 10,000k bulbs for a tank yet the plant specific pet store bulbs that cost me a small fortune (25$) are 3700K
So I ended up with a 5000K, a 6500K and the 3700K bulb over one tank, and on the other I didn't care and wen't with two 13w CF 4100K bulbs

Plant growth seems to be very equivalent on both tanks except for the red plants. they prefer the tank with the 3 bulbs.
Now, what do I check to see what tank two is missing?
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mlody
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PostPosted: 2004.06.15(Tue)17:07    Post subject: Reply with quote

Well it looks like we have a few issues to addess here....

Quote:
Three reasons: 1) Color temperature ratings oftentimes seemed derived by manufacturers through black magic, 2) a single given color temperature can be derived in any number of ways owing to variances in the bulb's spectral output,


The 1st and the 2nd reason are very similiar in the idea that there is no single industry standard to govern the tests of these light bulbs. Each company differs in the ways they test their products to "fool" the consumers that they are buying a better product then their competitors. What better example then the
Quote:
The mystery spectrum belongs to the Hagen AquaGlo, which is rated at 18000K
Laughing
In fact, you can clearly see that even the same company can give diffrent (not quite relative to their other bulbs) Kelvin ratings for the bulbs they produce. You can see this clearly in the comparison of the various bulbs of GE. (Although the odd ball, 3200K rating, is a T8 and not a T12 which may account for the weird rating.

Quote:
color temperature gives you very little indication of a bulb's actual spectrum or lumen output, which are the more important factors in a bulb's ability to grow plants well.

The lumen output of the bulb has nothing to do with the spectrum of light it puts out. Its like comparing the speed of the car and the type of the car. The color temperature does have some (general) indication of the bulb's actual spectrum. If you look at the comparison list you will notice that the bulbs range from 5,000K to 6,700K (only a deviation of 1,700) which is not a very broad spectrum. If you look at the comparison you will see that ALL the bulbs peak at the green, yellow, and blue (farthest left) wavelengths. The biggest discrepency is in the red peak where things get a little messy. That can be taken to conclusion that the red peak is not a large factor in determining the color temperature between 5,000K and 6,700K. Some look more intense the other because.... .
Quote:
Although I haved tried to keep most factors constant while making the spectra, they are not to be taken as accurate because the instruments are not calibrated

The odd ball where you get a very intense light with many peaks is a T8 light bulb and not a T12 bulb. Methods will probably varry if one is to find the Kelvin rating in a T8 bulb (T8 bulbs have improved efficency and CRI ratings) and a T12 bulb. Although I cannot say this for certain because I do not know various companys' procedures on finding the Kelvin rating. Again this supports the idea of a unified procedure in obtaining the Kelvin rating. A comparison of bulbs from 3,000K all the way to 18,000K would probably the most useful data in this case



Quote:
overall appearances that differ widely (yellowish versus pinkish versus creamy white)! Why is that?

I like to think of this as a musical peice played on the piano. If you take filter out a certain frequency (say 20-120 hz) the song will not be the same and this is easily noticable. The general feel for the song will still be the same, but it will not be the same song. The same thing occurs in the light which is emitted by these bulbs. Look at the spectrum in the comparison chart and look at the color the person noticed. The bulbs that give off diffrent color of light (meaning what we see) when there is a shift in the peak or if there is a peak present/missing. This accounts for the diffrence in the apperance of the light. Bulbs that have very similar spectrums emitte a color of light that is quite similar (you can see that on this person's chart).

Quote:

Quote:
The Kelvin rating of a give bulb is a specification of the spectrum of light emitted by a given light bulb which is similar to an object of a given temperature. This has nothing to do with the human eyes, correct


No and no, for the reasons cited above.


I have always thought of the Kelvin rating of a light bulb same as the rating give to various stars in the sky. I may be flawed in this because the two could be very diffrent.... but, the question I pose is this. If the Kelvin rating is for the human eyes only then why would the color of the light vary so intensly? This would make the Kelvin rating of the light bulb a very impractical value since it says nothing about the color of the light emitted.

Quote:
And let's not forget that the designation of "actinic blue" is not a reference to color temperature but to the presence of a pronounced spectral output in the 400-500nm-wavelength range, usually centered around 420nm. What, for example, do you make of the Coralife Actinic Blue lamp, which is rated at 7100K?


When I said acintic blue in the previous post I was actaully thinking about the Coralife 7,100K lamp. It appears that things get a little strange when looking at the Kelvin rating of the lamp from various company. That is why you cannot depend on the Kelvin rating to know the lamp's plant growing ability, but it is still a nice refrence point (just like the wpg rule and inch per gallon rule).

Quote:
The quest for a high CRI (actually color rendering index) is, IMO, way overrated

I agree, but like you said this is a matter of personal opinion.

Quote:
You cannot accurately infer a spectrum from a given color temperature nor vice versa.

Yes you are correct, but you can still get a general idea of the kind of light emitted with the Kelvin rating; even though it is not precise.

So.... It appears that we have just totally destroyed the Kelvin rating of lamps in their plant growing ability... CRI would also never be a good idead, because this value is strictly of human eyes only. Anarchy! Razz
Going back a bit... if you look at my first post I use the words "Kelvin rating" and "correct light spectrum" interchangably. I should not written it this way, but for all general purposes I don't see anything wrong with that. (since the Kelvin rating SHOULD be a accurate rating of the spectrum emitted.)

This has turned into a quotefest '04... I didn't mean for it to turn out that way, but if I did not use quotes it would be hard to keeps things organized. Confused

LOL Discus Man, in an effort to clarify we made things worse Embarassed . Of the topic... This reminds me of when I clean, I usually make a larger mess before it gets better Wink . There are devices to measure the spectrum of light and the amount of lumens emitted, but this darn devices are just too expensive. Red plants require more blue then your traditional green patch. The 6,500K and 5,000K probably give off more blue then the 4,100K, but for the reasons above no one knows for sure. The only way to check this is to get a print out of the spectrums emitted and the their power.

BTW: the first picture did not load on my pc for some reason.
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2la
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PostPosted: 2004.06.15(Tue)18:35    Post subject: Reply with quote

mlody wrote:
The 1st and the 2nd reason are very similiar in the idea that there is no single industry standard to govern the tests of these light bulbs. Each company differs in the ways they test their products to "fool" the consumers that they are buying a better product then their competitors. What better example then the
Quote:
The mystery spectrum belongs to the Hagen AquaGlo, which is rated at 18000K
Laughing
In fact, you can clearly see that even the same company can give diffrent (not quite relative to their other bulbs) Kelvin ratings for the bulbs they produce. You can see this clearly in the comparison of the various bulbs of GE. (Although the odd ball, 3200K rating, is a T8 and not a T12 which may account for the weird rating.

So you agree: Color temperature is a very poor indication of anything?

Quote:
The lumen output of the bulb has nothing to do with the spectrum of light it puts out.

No one's said as much...

Quote:
The color temperature does have some (general) indication of the bulb's actual spectrum. If you look at the comparison list you will notice that the bulbs range from 5,000K to 6,700K (only a deviation of 1,700) which is not a very broad spectrum. If you look at the comparison you will see that ALL the bulbs peak at the green, yellow, and blue (farthest left) wavelengths. The biggest discrepency is in the red peak where things get a little messy.

I guess this will be the point at which we disagree most vehemently (at least on my end Wink). The unfortunate part of that light comparison is that the spectral outputs are given as emission spectra rather than in graphical form in which it would be easier to compare the relative intensities along the spectra. In the latter case you would be able to see the differences between strong narrow peaks and broader 'mountains' across a range of wavelengths. Let's look at the 5000K bulbs one more time. In order, they are:

GE Chroma 50
GE SPX50
Philips Advantage
Philips Ultralume

http://www.geocities.com/Heartland/Hills/2637/c50.jpg
http://www.geocities.com/Heartland/Hills/2637/gespx50.jpg
http://www.geocities.com/Heartland/Hills/2637/adv.jpg
http://www.geocities.com/Heartland/Hills/2637/ultralume.jpg
(Images may not be available; refer to this page for them.)

The last three look similar superficially, but appear noticeably different to the eyes (to reiterate a point about the the near-uselessness of color temperature ratings even to predict how they appear, which is the only thing they're suppose to indicate!). Even if we're to conclude that consistency among spectral outputs allows you to predict color temperature, you cannot claim the reverse to be true (that you can predict spectrum from color temperature)--because in walks the GE Chroma 50 who weighs in with a markedly different spectrum from the other three--yet it provides the same color temperature. Likewise, who would guess that a 7100K rating could be attributed to an actinic blue bulb? This leads me back to the statement that you cannot predict a bulb's spectrum from its color temperature. This would be akin to me telling you that the answer to an addition/substraction question is 100, so what is the math problem? Is it 50 + 50? 24 + 35 + 41? 80 + 2 + 12 + 0.4 + 5.6? 33 - 21 + 64 - 8 + 32? Or if I gave you a jar of green-tinted water and asked you to tell me what combination of dyes I used to obtain it? Just green? Blue plus yellow? Something else?

Quote:
That can be taken to conclusion that the red peak is not a large factor in determining the color temperature between 5,000K and 6,700K.

I don't think that's a very valid conclusion given that there are so many other confounding factors. Do you have an accurate impression of the less intense but broader components of the spectra? Or even the peaks? I wouldn't know where to begin to tell you how to quantify how one bulb's output in its green peak compares with that of another. The graphs are qualitative only, but even that's enough to tell you that there can be significant variances in spectral outputs for a bulb with any given color temperature. Again, color temperature is a poor indicator of anything.

Quote:
I like to think of this as a musical peice played on the piano. If you take filter out a certain frequency (say 20-120 hz) the song will not be the same and this is easily noticable. The general feel for the song will still be the same, but it will not be the same song.

This is not a reasonable analogy, though. A musical piece consists of distinct notes that can be distinguished from other notes. If you omit an entire range of notes, you change the entire overall composition (color temperature) quite markedly. What is not explained is how the overall composition (color temperature) can sound exactly the same (same color temperature) yet notes are omitted here, replaced there, added here and there. It doesn't work.


Quote:
The same thing occurs in the light which is emitted by these bulbs. Look at the spectrum in the comparison chart and look at the color the person noticed. The bulbs that give off diffrent color of light (meaning what we see) when there is a shift in the peak or if there is a peak present/missing. This accounts for the diffrence in the apperance of the light.

Let's attack this from another starting point: What does color temperature indicate? You would agree that it represents the overall color that radiates from a theoretical black body heated to a given temperature, right? Blue is blue, mauve is mauve, fuschia is fuschia. If that is the case, then the differences in overall color should be accounted for in the Kelvin rating, but clearly they are not--as you have described yourself in the above. This speaks most to Reason number 1) that I provided in my previous reply.

Quote:
Bulbs that have very similar spectrums emitte a color of light that is quite similar (you can see that on this person's chart).

Certainly, but that is not the crux of this discussion (it's in fact the corollary of the crucial question). The question originally was about color temperature being useful as a predictive factor in a bulb's ability to grow plants. This itself depends on the answers to more fundamental questions:

What are the most important aspects of a plant-growing bulb?
My contention is that it is spectral output and intensity. I don't know if you agree or not.

Does color temperature say anything about intensity?
You and I both agree that the answer is no.

Does color temperature say anything about spectral output?
It sounds like you're saying yes, but I don't want to put words in your mouth. I say no, for all the reasons I've provided already.

Is color temperature a consistent indication of anything?
I've said no and you've said no, that there needs to be standardization amongst the companies that are providing these ratings. I don't see how, then, color temperature becomes a mostly reliable predictor of plant-growing capabilities.

Quote:
I have always thought of the Kelvin rating of a light bulb same as the rating give to various stars in the sky. I may be flawed in this because the two could be very diffrent.... but, the question I pose is this. If the Kelvin rating is for the human eyes only then why would the color of the light vary so intensly? This would make the Kelvin rating of the light bulb a very impractical value since it says nothing about the color of the light emitted.

I don't know how else to say this, except...

Bingo! Wink

Remember that the various astronomical societies and universities hold their weights and measures to much higher and agreed-upon standards--it is the only way that the scientific method works. Fluorescent light bulb manufacturers are not subject to the same strict standards.

Quote:
When I said acintic blue in the previous post I was actaully thinking about the Coralife 7,100K lamp. It appears that things get a little strange when looking at the Kelvin rating of the lamp from various company. That is why you cannot depend on the Kelvin rating to know the lamp's plant growing ability, but it is still a nice refrence point (just like the wpg rule and inch per gallon rule).

You've parroted my sentiments exactly up till that last sentence, which is self-contradictory.

Quote:
Quote:
You cannot accurately infer a spectrum from a given color temperature nor vice versa.

Yes you are correct, but you can still get a general idea of the kind of light emitted with the Kelvin rating; even though it is not precise.

I prefer the term "rough idea" rather than "general idea," but otherwise I would concur. I would also add that not only is it not precise, it's not always accurate, either.

Quote:
So.... It appears that we have just totally destroyed the Kelvin rating of lamps in their plant growing ability... CRI would also never be a good idead, because this value is strictly of human eyes only.

I've been trying to do this for the last few years now--not because I don't believe in color temperature's potential utility in serving as a rough guide for aquatic gardeners, but because I see no consistency whatsoever amongst the bulb manufacturers. There are so many better parameters that could be provided and more easily standardized that it strikes me as a huge mystery as to why these are so often forsaken for much less useful color temperature information.

Quote:
This has turned into a quotefest '04... I didn't mean for it to turn out that way, but if I did not use quotes it would be hard to keeps things organized.

Nor did I, but it's the only way to keep things ordered to any degree.
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