Finding K ratings

[fish_4_all]

I am trying to find the K rating for a bulb I bought. I know, fancy names but it is about as bright as the other one I have in the fixture.

It is a 40 watt, GE 48" Ecolux plant and aquarium F40. 1900 lumens, cri:90, F40T12.
I know it really doesn't matter what it actually is but for the purpose of keeping records and tracking, it would be useful to know. That and if my plants do ok and then improve if I put 2 GE daylight 40's in the fixture instead of one and my plants take off then I at least have something I can share that might help here.

If anyone can tell me the K rating, it will help. If anyone has a site that tells the k rating and lumens of all lights, that would be even better.

edit: Well, I guess Malkore already got this one before. 9325K is the guess on the rating. I actually found an answer to something I wanted in a search.

Anyway, that is one bulb, and is still a guess so a site to find this information would be extremely useful to all of us.

 

[BlazerFRS]

Looking thru the GE e-catalog the "ecolux" seems to equate to 5000K but not sure about your specific bulb.

 

[fish_4_all]

http://www.wetwebmedia.com/marine/setup/lighting/

This is a site I found, if anyone looks at it, let me know what you think. It has an interesting statement about CRI levels needing to be 90+ for good plant health.

 

[Jchillin]

This particular statement is quite useful:

Color Temperature Color Temperature is a more difficult concept to elucidate. For our purposes, let's just say that this is an equivalent temperature of a star (like our sun) that would emit the radiation measured. Our stars sunlight ranges somewhere between 5,000 and 6,200 degrees Kelvin. We want a light source of 5,000 degrees Kelvin (some writers say 6,000) or greater along with a CRI of 90 or greater. Make sense so far? Let me re-emphasize; the pretty color rendered by "aquatic fluorescents" has nothing to do with functionality. You want a CRI of 90+ coupled with a Color Temperature of 5,000+ Kelvin.

FWIW, malkore has a nice sticky on lighting which emphasizes basic minimums of light for planted tanks.

 

[CGGorman]

Just FYI...CRI stands for "Color Rendering (or rendition) Index".

6500-6700 Kelvin is widely considered the ideal color temp to simulate natural sunlight on an overcast day. It is use to calibrate all the professional video equipment in the world. Higher than about 6700k starts to look bluish. A high CRI ~should~ equate to a bulb with similar spectral balance as natural sunlight, at a color temp of around 6500k. Makes sense that these bulbs would suit plants...

http://en.wikipedia.org/wiki/Color_rendering_index

 

[malkore]

But the CRI number is what really matters. The higher the CRI, the better. A cri of 90 is a great plant bulb. I've seen a few at 94 too.

 

[CGGorman]

Agreed. A high CRI equates to a very balanced spectral output.

 

[fish_4_all]

Well I am totally confused then then. If my Ecolux turns out to be 9325 with 90 cri then what does that mean? Does it just say that I have a bluer looking tank with proper light levels or is the K too high? Is the 6500k light I got that says natural daylight but has a cri 75, is it too low or will the K rating compensate?

Lets forget about watts per gallon for the time, what is the best bulb? 6500k with a 90+cri? 5500 with a cri of 95? Anything above 5500k with as high a cri as you can find? Would it be best to put 4 different bulbs in a 4 light fixture that have all different K higher than 5500 and a cri as high as we can possibly find them?

Just one other observation: the article says that our sun doesn't emit K higher than 6200K. Do we exceed that to allow for max penetration in water or is anything over that a total waste of money?

Edit: http://www.gelighting.com/na/busine...ental/downloads/EcoluxProductListing82005.xls

Here is the best GE list I have found

Unfortunately, it says that my GE Ecolux that looks so good and has the high CRI of 90 is only 3100 K. So much for a good light unless the K rating actually doesn't mean anything and it all rides on the CRI. And it says it is better for plants. Hmmmmmmmmmmmmm.....

Anyone more confused yet? LOL

 

[Wizzard~Of~Ozz]

What numbers are on the bulb? it should have

F??WT?/???/ECO

Also, it will have the K of the bulb written on it.

http://www.gelighting.com/na/busine...oads/fluorescent/28345_starcoat_t5_linear.pdf
Those are the T5 bulbs (complete with Spectrals)

as for CRI. Colour Rendering Index, while informative, typically has no value to plants, it's mainly how your eye percieves the colours emitted by a bulb. (ever shine a red light on a red object and it looks white?) so CRI is visual spectrum completeness.. plants don't have eyes, so while it's a "complete" spectrum, it may not have the intensity for plants. case and point, an incandescent bulb has a CRI of 100, but you couldn't even grow algae with it.

If you want the "BEST" bulb, then you'ld have to go MH.. but that's not pratical.. so to answer the question, the best bulb will have a temperature of between 5000k and 6500k (typically the most balanced) and be tri-phosphor type (if you notice the spectral graphs I posted, you will see 3 peaks in the spectrum, three= tri-phosphor or often called "full spectrum". the thoughts above are on the right track, but CRI is visual, and our plants don't care what we can see.) I'm not saying a 9325 bulb won't work, because it will. It must be tri-phosphor tho.

 

[fish_4_all]

So the CRI doesn't matter but the bulb I have is only 3500K. Why does GE say it is one of the best lights for growing both aquatic and land plants? 3500K doesn't even come close to the supposedly needed 5500K+ that is needed to grow plants. Why do so many use it and have great success with it with such low K?

Is it a strong statement that K isn't as important as CRI or is it something else that makes the bulbs work so well to grow plants?

 

[Wizzard~Of~Ozz]

Does the bulb state it's 3500K or is this asumed? The EcoLux is a brand, similar to Philips Alto.. it's Eco(Enviroment) Lux (Light).. it doesn't have as many harmful chemicals in it (typically mercury I believe).. Alto are marked with green caps.. same concept. they are available from 3500-6500k (perhaps higher)

The K isn't as important as the Spectrum. Eco lux regardless of the temperature have a very good spectrum, the temperature just alters the balance of reds-blues.. They are also Tri Phosphor bulbs (meaning they have spikes in 3 different regions of the spectrum), Red, Green and Blue, all of which are required for photosynthesis. The balance of reds and blues should be close (hence 5k), however the deeper the water the more inclined I'ld be to think reds play a larger role.. but I still have to research this.

 

[fish_4_all]

3500K came straight form GE, and is also on the link I posted earlier.

I don't know what to think. All I know is I am going to try them and if they work then hey, I must have done something right. Will keep everyone up to date. I am taking pictures daily.

 

[Steve Hampton]

So the CRI doesn't matter but the bulb I have is only 3500K. Why does GE say it is one of the best lights for growing both aquatic and land plants? 3500K doesn't even come close to the supposedly needed 5500K+ that is needed to grow plants. Why do so many use it and have great success with it with such low K?

Two reasons. First, they are marketing lamps, hype is good for this concept.

Secondly they are being factual too. Those lamps will produce good plant growth, just maybe not the type of growth you'd like and the color of the lamp may be very attractive over a planted tank. Personally I'd never use the lamp except in combination with other very blue lamps. There is so much misinformation and worrying about lighting and it absolutely puzzles me why? There are so many other factors that effect lighting rather than a bogus Kelvin approximation or CRI that those two "numbers" pale in any real significance. By far, the choice of reflector matters the most...it doesn't matter what color or spectrum of lighting is over the tank if it isn't getting into the water at the right angle and is lost to restrike and deflection. Ballast Efficacy Factors play a huge role in whether the combination of lamps and ballast will produce what the manufacturer claims. That is a key phrase. Manufacturer claims...A fluorescent lamp produces an interrupted spectrum of light, not a continuous spectrum like a theoretical blackbody radiator. So at best, Kelvin ratings on fluorescent lamps are approximations...at worst they are a number drawn out of a hat from a manufacturer. For example, compare a 10000K PC to a 9325K PC...huge difference in color. Heck I can place two 6500K lamps side by side with different ballast or from different manufacturers and see a startling difference in color. Because a Kelvin rating for a fluorescent lamps is an approximation and is made up from combining different color producing phosphors powders the same 6500K lamp could be composed of every differing wavelength combinations. Much like the combinations of coins to arrive at a dollar...they all equal a dollar but the make up of the dollar (100 cents) could be quite different...2 quarter, 4 dimes, and two nickels, 3 quarters, 2 dimes, and 1 nickel...with the coins representing red, green, and blue wavelengths. That's why we may see one lamp with a rating of 6500K having 2300 lumen's and another having 2450 lumen's...the second one has more green wavelengths. Lumen's is a measurement skewed for the human eye and so green appears brighter to us...but to plants...Plants don't give a rip and probably laugh at our concern over lighting. After all they know that the kind and "color" of lighting reaching them is constantly changing due to organic solutes in the water (attenuation), turbidity, shading, depth from surface due to rising water from heavy rain, runoff of producing silt, movement of the sun, cloudy days, competition and shading. The point is it seems likely that plants have to be highly adaptable and probably don't have a "sweet spot" where lighting is best. I've always focused on providing ample lighting that renders colors pleasing to me (I'm with Travis on using Actinic if possible) and concern myself with CO2 levels and nutrient dosing...those have far far far greater impact on growth rates, leaf color, and overall health than the CRI or Kelvin claims of a lamp manufacturer.

Just my two cents.

 

[fish_4_all]

I like your two cents worth, but I would say it's worth a dollar. Is the way I would base my lighting on my tanks and is the way I am doing it right now. The tank is bright and it looks good. Will my plants grow, we will see. If they do then the lighting stays, if not, I will change the lighting, real simple. I have not added CO2 yet just to see how the plants will do and I don't have a diffuser set up yet.

I also agree with the deflector being important. The first fixture I got was white and the inside was white. While it did reflect some light, when I switched to the stainless steel one, the lighting increased a ton with the same bulbs.

I do think that ultimately the numbers matter, but as far as what is being told to use by the manufacturer, not a chance. Make your base purchases on the numbers and if they don't make the tank bright enough then take them back. If the color isn't right, take them back.

Make the tank bright and plants should grow, make it look good and you will want to keep your tank looking good. Dim light that doesn't look good results in a tank that you ignore and won't take care of.

Case in point, my 2 10 gallon tanks. The lighting was ok but not bright, and the plants were a hastle to maintain and keeping the leaves cleaned up was a pain.

Now my tank is brightly lit. I like to look at it again. If my plants grow better it will be even more rewarding because I will enjoy caring for my plants and spending a little more time to make sure they are thriving. After all, if you like a bright room you wouldn't put one 10 watt light in it and paint it with a dark light absorbing color and expect to spend any time in there, would you?