CRI test and Mcree weighted results

[Rahz]

These tests were conducted with Citizen 1825s but results should be similar for other brands with similar SPDs. The SQ-520 was used for measurements, and while it's the best low cost solution at the moment there's still a difference between the reading and the reality. Those differences were not factored in for this test but it should still provide a good idea of the differences in output based on phosphor coating, and hopefully an idea of how plants will react to particular spectrums within the test range based on the Mcree data.

4 chips were placed in a 12" square and placed approximately 18 inches from the sensor. Total system wattage was identical through all results.

Preliminary PAR test results
3000K70CRI 950
3500K80CRI 921
3000K80CRI 905
3000K90CRI 856
2700K90CRI 780

The 3000K 70CRI chips are putting out the highest PAR numbers, followed closely by 3500/80. At the bottom of the list we have 2700K emitting substantially less photons than the winner.

But if the Mcree curve describes the absorption chance of a photon at a specific frequency we can weigh the results and hopefully get a more accurate gauge of the chips photosynthetic potential. The following information is based on an interpretation of the Mcree chart. In that study there were 6-7 test samples that had roughly the same shape with minor and symmetrical variations. The rest of the samples were thrown out. The SPDs of each K/CRI combination were digitized along with the Mcree data. Each 5nm range is given a percentage of total output value which is multiplied by the Mcree data(percentage change for absorption of a photon). The average absorption rate of each spectrum is multiplied by the par reading to get what hopefully will be the total PAR absorption for the spectrums.

Conversion factors for plant response from 400-700nm. These numbers represent the absorption rate of each spectrum.
3000K/70CRI 78.034
3000K/80CRI 78.229
3500K/80CRI 76.566
2700K/90CRI 80.460
3000K/90CRI 78.355

2700K/90CRI has the best chance of being absorbed by the plants which was expected, but surprisingly the rest aren't far behind and 3500K/80CRI is coming in last.

Here are the Par values multiplied by the conversion factor.
3000K/70CRI 741
3000K/80CRI 708
3500K/80CRI 705
2700K/90CRI 627
3000K/90CRI 670

In this final result we see the 3000K/70CRI sample staying in the lead. Could it be that 3000K/70CRI produces the most photosynthesis?

Observations: In removing several Mcree test subjects as anomalies the slight hump in blue was subdued. Had I used a more comprehensive average the 3500K/80CRI and 3000K/90CRI would show slight gains but I wouldn't guess they would match the winning figure. I may go back and use new values with a more strict interpretation of the Mcree curve to find out how much of an effect it would have. Regardless of that issue 2700K/90CRI it seems is the loser who's superior spectrum just can't make up for the phosphor induced output deficiency... but it must also be considered that the sensor is placing a penalty on the high CRI samples, both 2700 and 3000K. Anyway, results were surprising to me, both spectrum absorption rates and final results. Does the methodology make sense? And thoughts or criticisms?

 

[Rahz]

Thinking a little more about this, there's a spread from 627 to 741. If the blue values in the Mcree data are raised a bit that would benefit the 3000K/90CRI and the 3500K/80CRI. If the red values were adjusted to compensate for the sensor that would benefit the 3000K/90CRI and the 2700K/90CRI. Put all that together and the spread is reduced. How much I'm not sure. I will go back at some point and adjust both and re-run the calculations. I'm pretty confident the sensor conversion would provide more accurate numbers but am unsure whether including the anomalies from the Mcree tests would make the number more or less accurate.

 

[CobKits]

i wonder, im not sure of the validity of average response coefficient vs par readings for 2 reasons which you alluded to:
-response coefficient doesnt account for relative adsorption per wavelength which seems significant in this study
-most par meters fall off sharply and 700-730 absorption seems to have plant response, photosynthetic or not. 90 cri takes a beating here and i personally think we havent seen enough 90 cri real-world data yet to dismiss it.

 

[wietefras]

Nice work! So the McCree correction basically doesn't change anything really. Which was to be expected since the spectral distributions aren't that different.

When you talk about McCree and absorption, are you talking about the McCree Absorptance chart which shows how easily a certain wavelength absorbed or reflected by the plant? Or did you use the McCree RQE chart which shows the relative quantum efficiency for photosynthesis per wave length? I'm assuming the latter, but your terminology makes me wonder.

BTW Odd that in your measurements the 70CRI came out as producing substantially more light than 80CRI. Some other Citizen (horticulture lighting) figures shown here a while ago listed the 80CRI's as being more efficient. Which doesn't make sense though. So your numbers actually make more sense than Citizen's numbers did.

Perhaps you could correct the original PAR figures for the Apogee response curve like you did with the McCree curve. Although it's a different calculation since the Apogee curve goes to 0 for the longer wavelengths below 700. It's more like the lumen to PAR conversion which alesh did.

 

[Rayne]

For the sake of the discussion: Here are the spectral charts for the CLU058-1825 COB.

70 CRI: More blue. Might be best for the vegetative phase


80 CRI: The middle ground between blue and red


90 CRI: More red. Might be best for the flowering phase

 

[ttystikk]

Great stuff here, I can't help but wonder what the plants themselves think. Theory vs real world validation, which are the most significant factors in actual plant growth?

 

[weed-whacker]

4000k 5000k?


Thanks

 

[Johnnycannaseed1]

Good test Rahz and well presented. Only one slight problem Keith McCrees data is flawed :-

In his experiments he tested the effects of "monochromatic" using an "extract of a leaf" as opposed to an "actual leaf" and "non-monochromatic" light source, think about that for a second and the possible implications.

And thus this is how the grow world came to get those two crazy A/B peaks which should in theory grow anything perfectly (according to the flawed data) ...Yet it neglected the effects of the other chlrophyll accessory pigments, let alone the differences between C3 and C4 plants (different light harvesting systems), or the fact that "individual" C3's and C4's have different light requirements (Don't forget light is food) and just as some plants like high potassium whilst others prefer lower, you will find it is the same with plants and light ...some prefer a blue bias spectrum whilst others prefer a red bias - stage of growth will also have an effect.

So McCree data is completely flawed because it fails to take into consideration the many different variables and only tells part of the story, therefore it cannot be relied upon as a one fits all answer or even part answer for that matter (I mean what was the leaf extract from, was it canna?), his experiment leaves you with too many questions rather than actual answers ...or at least that's my opinion of his experiment based on real world tests.

 

[Malocan]

first thanks for informations,
im not sure if your par readings are correct, according to citizens pdf.
this pdf show other par #, 2700k 90 cri > 3000k 90 cri
3000k 80cri > 3000k 70 cri

Now i wonder which par# are correct, i think atm i trust more this pdf

 

[hillbill]

Lots of good thoughts there. PAR watts alone can be very misleading for cannapurposes as we all tend to want more proportional reds than natural light to flower with. It's our function to absorb best knowledge and combine that into a workable lighting solution in our unique situations and plants that may prefer somewhat different light as they prefer different soil moisture etc.

 

[bri77]

Doesn't PPF give an unfair advantage to the 70 cri chips because it stops counting after 700? But we know (or do we?) that there's lots of useful light just above 700? So 90 cri has a big chunk of useful light uncounted by PPF.

Any of that correct?

 

[Rahz]

@bri77, I have spectrum data up to 750, but didn't use it because the par readings don't reach that high. I don't see it as a major issue because even the high CRI samples don't emit more than a few percent above 700. I could get a conversion factor for the entire spectrum (that would slightly favor the high CRI samples) but there would be nothing to use it on. The par meter however does favor the lower CRI samples though and that's something that can be corrected.

im not sure if your par readings are correct, according to citizens pdf.

It could be a flaw in the sensor readings... which I can correct but will take a little more time.


@Johnnycannaseed1, The Mcree study provides a full spectrum response and isn't the classic red/blue peaked chlorophyll response. There are other issues with the study but it's what we've got to work with.

@wietefras @CobKits, Yes the values used are the RQY values, which seem like the right ones to use. High CRI did take a beating but I don't think it's because of the Mcree data. Had I use the full test set the blue bump would have benefited 3500/80 primarily and also 3000/90, but the change would be slight. The real issue is the Apogee curve subduing the deep red and exaggerating a portion of the lower wavelengths. I really should have normalized the test responses before manipulating them further as I think the difference would be notable and that seems to be what everyone else is noticing. So that's what I'll do at some point. I've put myself behind working on this project but I'll try to get back to it in a couple days.

 

[Rahz]

4000k 5000k?
Thanks

I had only so much to spend. If someone want's to spring for them, I'll build them, test them and then ship to owner. In lieu of that I could at least get a Mcree conversion factor from the SPDs to see how they compare. More data plotting (yay!) but it would be interesting to see how it comes out.

 

[CobKits]

ive got 4000 in 80 and 90 and 5000 in 70 and 80 that i can send over

 

[weed-whacker]

ive got 4000 in 80 and 90 and 5000 in 70 and 80 that i can send over

im seriously considering 4000k 90 cri or even 5000/6500k with/without 660nm monos

 

[CobKits]

@wietefras @CobKits, Yes the values used are the RQY values, which seem like the right ones to use..

i understand that but it seems to me that this might be faulty logic:

"The average absorption rate of each spectrum is multiplied by the par reading to get what hopefully will be the total PAR absorption for the spectrums."

again i may be overthinking it, but it seems like this would be double counting the spectrum/absorption effect, in other words, every spectrum is different and then you throw a factor on top of that, it would seem to over-emphasize that portion of the data

The real issue is the Apogee curve subduing the deep red and exaggerating a portion of the lower wavelengths. I really should have normalized the test responses before manipulating them further as I think the difference would be notable and that seems to be what everyone else is noticing

i can loan out a li-cor li-190 if you want to use that for the next test

 

[wietefras]

Good test Rahz and well presented. Only one slight problem Keith McCrees data is flawed :-

In his experiments he tested the effects of "monochromatic" using an "extract of a leaf" as opposed to an "actual leaf" and "non-monochromatic" light source, think about that for a second and the possible implications.

And thus this is how the grow world came to get those two crazy A/B peaks which should in theory grow anything perfectly (according to the flawed data)

Incorrect, it's the people who only look at chlorophyll absorption who think Blue and Red is all you need. McCree also shows quite high efficiency in all wavelenghts.

Even Citizen showed up with their datasheet implying that, for horticulture, the wavelengths between 510-610 should be ignored. That's burple talk.



McCree puts this notion to bed. So yes, the burple crowd is obviously been proven wrong. At best you can use that for additional lighting in greenhoues which already get most of their light from the sun.

McCree is still the standard. Although by no means is this supposed to be a light recipe.

So McCree data is completely flawed because it fails to take into consideration the many different variables and only tells part of the story, therefore it cannot be relied upon as a one fits all answer or even part answer for that matter (I mean what was the leaf extract from, was it canna?), his experiment leaves you with too many questions rather than actual answers ...or at least that's my opinion of his experiment based on real world tests.

Everybody in horticulture works with those McCree charts (RQE + Absorpance). PAR meters are based on that chart. Yet you claim it's "completely flawed". You will have to provide some evidence on that and also show what everybody should be using instead. It's a bit useless to say everything is wrong if you can't suggest something better.

So far the Emerson effect has been shown to exist, but other than that it's pretty much "every photon counts"

 

[wietefras]

im seriously considering 4000k 90 cri or even 5000/6500k with/without 660nm monos

Based on these results CRI90 costs you about 10% in light and CRI80 5% compared to CRI 70.

 

[CobKits]

So yes, the burple crowd is obviously been proven wrong. At best you can use that for additional lighting in greenhoues which already get most of their light from the sun.

odd that those same spectrums are yielding great fully developed plants indoors

 

[Sativied]

And thus this is how the grow world came to get those two crazy A/B peaks which should in theory grow anything perfectly (according to the flawed data) ...Yet it neglected the effects of the other chlorophyll accessory pigments, let alone the differences between C3 and C4 plants (different light harvesting systems), or the fact that "individual" C3's and C4's have different light requirements (Don't forget light is food) and just as some plants like high potassium whilst others prefer lower, you will find it is the same with plants and light ...some prefer a blue bias spectrum whilst others prefer a red bias - stage of growth will also have an effect.

So McCree data is completely flawed because it fails to take into consideration the many different variables and only tells part of the story, therefore it cannot be relied upon as a one fits all answer or even part answer for that matter (I mean what was the leaf extract from, was it canna?), his experiment leaves you with too many questions rather than actual answers ...or at least that's my opinion of his experiment based on real world tests.

Good post.

Additionally the results of a single leaf still gives a very incomplete picture of the results on a plant with more than one leaf layer. The MCCree curve is cherrypicked over more complete info but ironically it only shows what a poor choice 3500k is.

Notice the ~450 an ~660 in the blue graph (and the ~625, matching very well with cri 90).

Blurple led manufacturers didn't make up any wavelengths. They, like the naysayers now, cherrypicked a few graphs they thought they understood and used those to convince themselves and others.

If anything, what both show is that 3500k (as a color temp, not perse individual cob....) is a poor choice. Red should be highest, rest only enough. It's that last part where plant species differ most, and what we don't know exactly. There's no reason to choose so much blue and green, it's far less efficient for the plant. 2700k cri 90 is a good alternative to a more expensive WR led light (the ideal for now).

The blue YPF curve above still does not account for the effect blue has on the accumulation of different accessory pigments and vice versa, and does not account for the effect of for example FR on photosynthesis throughout the crop rather than measuring a single leaf. In reality that blue light become less efficient much faster than red (ironically making red even more efficient relatively...).

I don't see it as a major issue because even the high CRI samples don't emit more than a few percent above 700.

Funny how the value of a "few" % more or less light fluctuates so fast around here to suit one's preconceived notions. Compare those "few" % beyond 700 of the orange curve to the ppf difference in % between cri80 3000k and the cri90 2700k... in Malocan's post.

Obviously the difference in light output is so small already either way. Obviously your posts reek of bias towards 3500k. Obviously the 3500k lights people have above their plants and the ones you sell are not more efficient or higher in output than what's possible with 90cri. That is far more a matter of cob brand/bin/version/amount/driver. Letting that dictated the spectrum for plants for a grow light that should last for more than a few years is just... unwise.

Even Citizen showed up with their datasheet implying that, for horticulture, the wavelengths between 510-610 should be ignored. That's burple talk.

That's just where you connect the dot to, to blurple, appareantly the only thing where the line attached to in your limited reference frame. Doesn't mean it has anything to do with blurple, just means you have a few gaps in your knowledge and playing the one-eyed king parroting riu nonsense at the dutch forums has "grown to your head"... Citizen isn't the only one who suggested something very similar and has nothing whatsoever to do with burple.