LED Lighting Compendium

[OVT]

Great information. TY for the time and effort involved.

Any CRI data?
If a red tiger lotus looks blue under a specific LED fixture, I might have an issue regardless of everything else

[CalmSeasQuest]

Great thread - Thanks for all the work!

I just ordered the 36" TrueLumen Pro 8,000K for use over a 12 long. I expect the actual 8,000K PAR numbers to be slightly higher than reported as the tests conducted by AquaNerd used the marine version and the MQ-200 underestimates PAR when measuring very blue light by up to ~20%. I'll share PAR data once set up if interested.

[NWA-Planted]

Very very very awesome thread thank you for putting this all together!

Sent from my DROIDX using Tapatalk 2

[CalmSeasQuest]

PAR results for TrueLumenPro 8,000K

PAR measurements taken with an Apogee MQ-200.



These PAR measurements were taken in "open air". Based on my experience, they will differ little when measured with water in the tank. The fact that these lights use surface mounted emitters without any optics might provide different results through water - I'll remeasure once the tank is wet.

More photos in my 12G Long build thread.

[tank0211]

Originally Posted by Lowe

Remaining fixtures:

I'm considering the 16" fixture for a 24" long tank & would like to know if these front to back PAR measurements can also be applied off of each lengthwise end of the light as well?

[Hoppy]

Originally Posted by tank0211

I'm considering the 16" fixture for a 24" long tank & would like to know if these front to back PAR measurements can also be applied off of each lengthwise end of the light as well?

No, those numbers won't apply off each end. The reason is that off to the side there are several LEDs contributing light to any spot, but off the end, the number quickly becomes only one that contributes light. And, that is because LEDs far from the spot where you are measuring PAR have most of their light reflected off the water instead of refracted down into the water. This is also why the ends of the tank, even with a full length LED light, don't have as high a PAR as the center of the tank.

It would be nice to have the charts for lengthwise distances too. I'm sure they are available.

[tank0211]

Originally Posted by Hoppy

No, those numbers won't apply off each end. The reason is that off to the side there are several LEDs contributing light to any spot, but off the end, the number quickly becomes only one that contributes light. And, that is because LEDs far from the spot where you are measuring PAR have most of their light reflected off the water instead of refracted down into the water. This is also why the ends of the tank, even with a full length LED light, don't have as high a PAR as the center of the tank.

It would be nice to have the charts for lengthwise distances too. I'm sure they are available.

Thanks for the reply Hoppy. That's pretty much what I suspected though being that there are only 2 LEDS on the short lengthwise ends to contribute where as there are 44 on long sides of the 16".

I'm very interested in knowing these numbers. Maybe Lowe could get them for us?

[samamorgan]

Just a quick update to let you all know that I probably won't update this for a while. Things in life are hectic right now and I simply don't have the time to pursue the research and recreational activities that I usually do. I've been pretty absent from these forums for the last month and this is going to continue for the forseeable future.

[Hoppy]

Originally Posted by samamorgan

Just a quick update to let you all know that I probably won't update this for a while. Things in life are hectic right now and I simply don't have the time to pursue the research and recreational activities that I usually do. I've been pretty absent from these forums for the last month and this is going to continue for the forseeable future.

I'm really sorry to hear this. I'm sure this is up to date enough to go without a lot of revisions for several months. Good luck settling things down.

[CalmSeasQuest]

Originally Posted by Hoppy

I'm really sorry to hear this. I'm sure this is up to date enough to go without a lot of revisions for several months. Good luck settling things down.

+1 Thank you for all your work on this.

[madness]

The great thing about the internet is that if you get the ball rolling on a project then often times one or more people can carry the project once you are done with it. Often times it just takes that person to do the initial work and make it seem less intimidating and then other don't feel so afraid to get involved.

[JoeD323]

Originally Posted by samamorgan

Not all spectrums are created equal!
Analyzing photosynthetically active radiation (PUR)

Please keep in mind that the following is purely informational, and should be taken very lightly if at all when considering an LED fixture purchase!

One of the reasons LEDs can be so much more efficient than T5, compact flourescent, and even metal halide is spectrum output. The chlorophyll pigment is green in color, which means that it reflects the green spectrum of light to our eyes so we see it as green. This means that it absorbs all other spectrums of visible light. Check out this graph:
Attachment 40237
As you can see, plants absorb visible light very well between ~400-500nm and ~650-700nm. The absorbtion rate drops off significantly in the green and yellow spectrums. Here are some LED emmiter comparisons in terms of specrum. Big thanks to redfishsc for doing the footwork on this. Notice that the warm white LEDs put out significantly lower blue spectrum spikes, but much higher red-yellow spectrum spikes. Essentially this tells us that cool white LEDs are almost always better for plant growth.

LEDs put out very specific spectrums of light, which are defined by the manufacturer. LED manufacturers can fine tune emmiters to put out exactly the spectrum specified by the client. Since PAR meters measure light between 400-700nm, an LED array putting out less par than a broad spectrum flourescent fixture may actually be putting out more photosynthetically usable radiation (PUR).

Why is this concept important?
Say two LED emmiters read around 100 PAR on a meter. The first LED spikes highest in the 550nm range. The second LED spikes highest in the 450nm range. So while both emmiters have the same PAR value, emmiter two would actually grow plants very well because it is in a range that can be absorbed by the plant, while emmiter one would probably keep plants limping along, if they could even survive.

So I get the importance of PAR ratings vs depth and all that, but I am still a bit confused.

It is my understanding that plants (and even corals) are best able to utilize yellow light (in the 65-10K area) yet corals show best color in the actinic 14-20K range and that's why those are the ranges most commonly used for corals. Right? And the whole watts per gallon thing gets thrown out the window when discussing LEDs, anyway. Right?

So my question is this: Regardless of PAR ratings (which seem to be ridiculously high in most cases because the lights are meant for reefs), aren't the vast majority of LED fixtures on the market relatively useless to the planted tank keeper because of the spectrum they put out? In other words, before taking PAR into consideration, shouldn't we be first looking at spectrum?

Sorry if we already went over this or if I am confusing the subject lol I am having trouble wrapping my head around it.

Joe

[Hoppy]

Joe, we have lots of people successfully using LEDs to grow plants, so they can't be said to be ineffective. Most of us use "cool white", possibly with some "warm white" or "neutral white" mixed in. Those aren't really specifications, just general descriptive names. If you look at the spectra for a few cool white LEDs, for example, you find that they look very similar to each other. So, it is pretty safe to say that cool white LEDs are good plant lights.

The whole point of using PAR to determine how effective a given light is for plants is that the PAR is the light intensity in the band of light that plants respond to. So, PAR is the measurement of how much light, you get, in the spectral range that plants can utilize. It is also a mistake to assume that because chlorophyl absorbs blue and red light well, means that plants don't absorb other colors. They do, but they also reflect more of the green and yellow light striking them then they do the red and blue light. If you were to try to grow plants with just yellow and green light, you could do it. And, if you were to use the same PAR intensity for the yellow and green light as for blue and red light I suspect the plant growth would be comparable. I have seen no reports of tests to try to determine if that is true, for typical aquatic plants, so all we can do is guess.

[JoeD323]

Thanks for clearing that up Hoppy. I think I get it now. It all kinda makes me feel a lot less knowledgeable than I did yesterday lol

I work at an aquarium shop, and we cater to everything from goldfish and betta bowls to high tech planted and reef set-ups. I just got this overwhelming guilty feeling for some of the advise I've given people coming to me for help. Its funny cause I'm supposed to be one of the plant guys at the store yet now I feel like I've been steering people in the wrong direction when it comes to LEDs and t5 replacement lamps/fixtures.

I guess I've been stuck in the old ways when I thought I was up on the new teaching and logic on the subject. So, just so I am clear on all this...

PAR ratings refer directly to available light, regardless of spectrum, but are all of these bands of light usable (PUR)?. And plants can in fact utilize the white light put out by 10K bulbs as well as they do the 65-67K ones? Also, since plants absorb the blue and red spectral range, is it safe to say that actinic and 50/50 lamps are more useful in planted applications than I was originally taught?

I also have a question relating to the above breakdown of the TrueLumen fixture's PAR ratings. That fixture only puts out 8000K light, correct? Correct me if I am wrong, but is a single spectrum of light (in this case 8000K) sufficient for plants to thrive? I was under the impression that it was better to have several different spectra of light available to the plants for photosynthesis. For example, I am currently running both 6700K and 1000K t5 lamps over my plants for this reason. So what I am asking is: Are these fixtures marketed at a specific spectrum worth the buy? I mean, based on everything we've said so far, it seems that the reason LEDs are so great is the wide range of wavelengths they put out, right? So when I see these TrueLumens, which ONLY put out 8000K, it seems to me that this fixture alone would not be enough to promote the growth we have come to expect from our lighting.

Sorry for all of the questions, I ask them as much for myself as I do for the customers I will be helping in the future...I take pride in giving the best advise in my area of expertise lol


Joe

[samamorgan]

Just checking in, and replying to your post Joe. Kelvin rating has nothing to do with spectrum. Spectrum generally determines the kelvin rating, but they are not related systems of measurement. Spectrum refers to the intensity of light at certain wavelengths. Wavelengths are the scientific measurement of light waves in nanometers(nm) at the crest of each wave of light, since light travels in waves of harmonic motion like other forms of energy like sound and electromagnetic radiation. So basically spectrum is the measurement of light intensity.

Now Kelvin or color temperature is the measurement of visible light emitted by a black body radiator as far as I understand. I don't fully understand the concept of kelvin, but I equate it more to light visible to the eye. Essentially color temperature is a measurement of visible color, as compared to spectrum which is a measurement of light intensity in the entire electromagnetic spectrum.

Now, another problem with trying to use kelvin as a base for usable radiation: the rating varies widely. Two bulbs with a completely different spectrum that emit completely different PAR ratings can have exactly the same color temperature. One can be just awful for plants and the other could be very good. This is also more readily apparent if you look at graphical representation of the kelvin color temperature scale. 10,000k can be pink, white, blue, blue-green, or any color inbetween. It's a fairly inaccurate way to try and measure visible light, and i actually prefer to use chromacity to try and accurately describe things, though it's a bit harder to use universally because color temperature is already prevalent on the consumer side of the lighting industry.

A good example of the difference here: The x-ray spectrum, which we utilize for the common x-ray imaging in hospitals, is far outside of the visible spectrum. You couldn't rate something like this in terms of kelvin because the spectrum emits no visible light. This is the same with the commonly known infrared and ultraviolet light spectrums. The others that are less though of as being light are gamma rays, radio waves, and microwaves. There are some pretty crazy concepts out there, gotta love college physics and chemistry. Time to go take some more derivatives that I will never use when programming!