CRI test and Mcree weighted results

Compared to 70CRI it's 10

JorgeGonzales said:

3000K80CRI 905
3000K90CRI 856

That's the only 80 vs 90 comparison @Rahz made, and I wouldn't consider ~6% "huge", or the peak shift from 600 to 630nm insignificant.

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it's :
3000K70CRI 950
3000K90CRI 856

And yes I do call that 11% "huge". While shifting 30Nm obviously has negligible effect.

It cost light to convert the blue base light to longer wavelengths. There is no free lunch. You will always lose photons.

Seeing how the plants don't really care if it's 600 or 630Nm it's a waste

wietefras said:

Compared to 70CRI it's 10
it's :
3000K70CRI 950
3000K90CRI 856

And yes I do call that 11% "huge". While shifting 30Nm obviously has negligible effect.

It cost light to convert the blue base light to longer wavelengths. There is no free lunch. You will always lose photons.

Seeing how the plants don't really care if it's 600 or 630Nm it's a waste

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I'm not so sure that this "photons is all that matters" is 100% factual. What we aren't looking at is the favorable conditions of the 90cri for the emerson effect. Personally from what I've seen 3000k 80 cri cree seems to be somewhat magical in the yield department and 90 cri 3000k citizen looks very promising indeed. We will all look back 2-3 yrs from now and know that these disscusions led to a revolution in indoor cultivation of Cannabis. Yes blurple will have its place but white light will be preferred simply because of its ease of use.

At the end of the day I don't think there is a wrong answer on warm white spectrum. I would be more interested in total extraction yield than carbon yield and I think plant health or the lack of it dictates this as much as anything. A balanced photo nutritional diet is important as well all other aspects making up an ideal environment.

Stephenj37826 said:

I'm not so sure that this "photons is all that matters" is 100% factual.

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I didn't say that.

Still it has been demonstrated in actual test grows that light spectrum has much less of an effect than light quantity. Especially if the spectrum differences are so minute.

The Emerson effect can only be judged after a large and controlled side-by-side test has been done. For now it's just assumptions.

Small tests with added FR light have actually shown more stretch rather than increased yields.

wietefras said:

I didn't say that.

Still it has been demonstrated in actual test grows that light spectrum has much less of an effect than light quantity. Especially if the spectrum differences are so minute.

The Emerson effect can only be judged after a large and controlled side-by-side test has been done. For now it's just assumptions.

Small tests with added FR light have actually shown more stretch rather than increased yields.

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Well I can say if I was growing wheat I would use low pressure sodium myself because of the fact that wheat isn't very discerning when it comes to light spectrum. On the other hand the more chemically complex a plant is the more spectrum sensitive it becomes . The Emerson effect is really more about ratios than specific wavelengths. We are as clueless about spectrum when it comes to cannabis as we are about the Emerson effect .

Oh I would love to see all 70 CRI's

From wikipedia on photosynthetic efficiency:

'24% of the absorbed photon energy is lost due to degrading short wavelength photons to the 700 nm energy level'

Basically the plant uses a process to condition each photon for use in photosynthesis. 700nm light hitting the plant doesn't require any conversion and therefore no additional effort by the plant. Higher wavelengths providing more efficient photons for the plant can further improve electrical efficiency as a result. Think of it as reducing unnecessary overhead for the plant by providing it pre-conditioned power.

Emerson effect summarily states that there are two distinct photosystems operating at different wavelengths (sub 660nm and greater than 680nm) that increase photosynthetic efficiency by working together.

These may work in conjunction or as a result of each other, who knows. Both point to advantages of using light heavily focused in the 600nm+ wavelengths. As efficiency improves with the lower CCT whites they will be able outpace the performance of higher CCT values. 3000k CCT will replace the 3500k as the darling if it hasn't already now.

Regarding CRI, it has a negligible effect unless it increases the light produced in the red wavelengths or increases overall photon output. That probably is the simplest way to put it.

Putting plant species adaptations aside, I think a very effective (and hopefully efficient as technology improves) light distribution for plant would be:

10% white - equally weighted broad spectrum consisting of 400-700nm. This is intended to prevent or minimize any morphology variation issues common with artificial lighting.

90% red - Linear distribution increase from 600nm to max intensity at 700nm. Intentions are to provide the most usable photons with the least amount of wasted energy and enable the Emerson Effect.

The goal is to produce the most amount of photons with a set amount of power using that distribution. For example, if a 200w electrical power limit was set, you may be able to most effectively provide that light using 3 25w 3000k 70 CRI, 2 25w 2700k 80 CRI, 5 3w 660nm, 5 3w 680nm, 15 3w 700nm.

Stephenj37826 said:

We are as clueless about spectrum when it comes to cannabis as we are about the Emerson effect .

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Which makes it even more useless to claim that CRI90 spectrum is better than CRI70 when you get much more PAR light from CRI70.

Of course it's good to investigate things like that (if we actually can with our small operations though), but I have seen large light color grow tests (not with cannabis) where the burple performed only 4% better than "white" light. That's what was supposed to be the most efficient spectrum vs white and there barely was a difference. 4% is not something we could even really measure in our hobby tests. It's well inside the natural fluctuation you will see between grows. The red/blue products were of inferior quality too though.

Personally I got pretty much the same g/umol values when using "2000K" HPS and now using Cree COBs 3000K.

It's all just guesswork. until side-by-side tests start showing definitively that these slight spectrum changes actually provide better photosynthesis efficiency rather than the loss in photons from the extra phosphor conversion.

wietefras said:

It cost light to convert the blue base light to longer wavelengths. There is no free lunch. You will always lose photons.

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Except you don't really always lose photons, you always lose energy. Not the same, and I'm not sure if anybody knows how big the difference is in quantum yield between different CRIs in modern phosphors. Probably @guod.

When I compared 80 to 90CRI quantum yield with Citizen's data, ie pure photon count, it showed nearly identical number of photons emitted at 3500K with either 80 or 90CRI versions, but of course the 90CRI has more of them outside of the 400-700nm band, so a PAR meters shows lower PAR in exchange for a different R:FR ratio, for whatever that is worth to a grower. I'd say it's individual choice at this point, based on beliefs about YPF, expected photomorphogenic responses, etc.

Here's an example of what I mean, I double checked this with @alesh since I was wary of the results:




70CRI in a cooler temperature though...oof. Everybody is always like but but but HPS is only 22CRI. Sure, but HPS's spectrum isn't 50% green and 25% blue light. Yuck and no thanks.

There's a lot of green in HPS spectrum, the only thing it puts out more of is yellow- and of course heat.

JorgeGonzales said:

Except you don't really always lose photons, you always lose energy. Not the same

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If anything, that shows what a mess those Citizen datasheets are.

In the CLU058-1825 datasheet they show 3000K 90 CRI being 9% less efficient than 3000K 80 CRI (1.94 vs 2.12 PPF/W)

Besides, I was talking about fluorescent conversion. The photons from the base diodes excite the phosphor and then photons of a higher energy level are emitted, but less of those. That's how it works. Adding more blue to correct for the lost photon count can also be done by going for a higher color temperature.

wietefras said:

If anything, that shows what a mess those Citizen datasheets are.

In the CLU058-1825 datasheet they show 3000K 90 CRI being 9% less efficient than 3000K 80 CRI (1.94 vs 2.12 PPF/W)

Besides, I was talking about fluorescent conversion. The photons from the base diodes excite the phosphor and then photons of a higher energy level are emitted, but less of those. That's how it works. Adding more blue to correct for the lost photon count can also be done by going for a higher color temperature.

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Sorry that is completely wrong. I started a thread specifically about this.

https://www.rollitup.org/t/phosphor-conversion-based-led-limit.911213/

Read through you'll see what I'm talking about.

You start with x blue photons a % of which are converted into lower energy photons by way of electron loss. Also known as stokes loss. You never gain photons and any 2 photons never combine. If the photon makes it through the phospor with all the "holes" line up it remains the same "blue" the rest drop electrons and at the end are higher in nm.

Also yes 90 cri is lower in the 400-700 nm range as the 90cri has more photons above 700. Does that make it inferior? I don't think so. 70 cri 4000k will be king if 400-700 nm photons is all that counts .

I'm digging this debate because I'm learning a lot.

Not going to wade through a 4 page bla bla thread. Look up "quantum yield" though.

The point is, 90 CRI is a lot lower in 400-700Nm range. That's what the plants use most. Indeed there is a bit extra above the 700Nm, but that can never compensate for the extra Stokes losses from going higher CRI.

ttystikk said:

I'm digging this debate because I'm learning a lot.

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Yeah... both sides of the conversation are presenting seemingly sound information.

Yet some might be forgetting the PAR meter settings favored the blue end of the overall par spectrum.

CLU 058-1825 70 CRI: More blue. Might be best for the vegetative phase


CLU 058-1825 80 CRI: The middle ground between blue and red


CLU 058-1825 90 CRI: More red. Might be best for the flowering phase

I have corrected the sensor response and used it to come up with new conversion factors. I have also taking readings at a different drive current to see if I could detect any reading errors. The two sets of readings are within 2% so I consider the readings good. There was an anomaly with the 2700K/90CRI samples but at best it would push the result closer to the 3000K/90 CRI result but not surpassing it.

Now, before I post the results I need to point out that correcting the sensor response includes not just a boost to deep red but a reduction in the mid range and a boost near 400. Apogee took all that into account when determining their base line because the results are largely unchanged.

Original conversion factors (corrected factors) for plant response from 400-700nm. These numbers represent the absorption rate of each spectrum.
3000K/70CRI 78.034 (78.110)
3000K/80CRI 78.229 (78.274)
3500K/80CRI 76.566 (76.653)
2700K/90CRI 80.460 (80.094)
3000K/90CRI 78.355 (78.130)

Here are the Par values (corrected par values) multiplied by the conversion factor.
3000K/70CRI 741 (742)
3000K/80CRI 708 (70eight)
3500K/80CRI 705 (706)
2700K/90CRI 627 (625)
3000K/90CRI 670 (669)

So correcting the sensor response resulted in almost no change to the results. I don't know about you guys but I'll be taking a closer look at 3000/70 and the other low CRI options. It's not the result I was expecting and doesn't seem intuitive but I don't suspect there are errors in the spreadsheet. I'll be glad to share the data if anyone is interested in playing with it or checking my results. The data also contains 705-745nm numbers for the Mcree curve and the 5 spectrums tested.

I also want to point out that these results aren't the definitive word on cob K/CRI. The results are exactly what I have stated they are. If there are other factors involved that will give high CRI a boost it can't be accounted for using the Mcree data. But, it does indicate that testing of lower CRI options should happen in a real world environment. I wouldn't be surprised if the results hold up. It wouldn't be that surprising if they didn't. Fortunately this Mcree comparison is only stage 1 of this project. We'll eventually have some real world results under the test lamps to compare with the numbers.

I am willing to bet the other stages of this project includes a single three way grow off using the same number of clones from the same parent plant, the same grow medium and nutrient program, the same number of COBs, power output/voltage/amperage, CCT, and the same amount of growspace. With the only variance being the CRI rating.

Yes, well 5 way grow off. Results will be in early next year.

Stephenj37826 said:

Sorry that is completely wrong. I started a thread specifically about this.

https://www.rollitup.org/t/phosphor-conversion-based-led-limit.911213/

Read through you'll see what I'm talking about.

You start with x blue photons a % of which are converted into lower energy photons by way of electron loss. Also known as stokes loss. You never gain photons and any 2 photons never combine. If the photon makes it through the phospor with all the "holes" line up it remains the same "blue" the rest drop electrons and at the end are higher in nm.

Also yes 90 cri is lower in the 400-700 nm range as the 90cri has more photons above 700. Does that make it inferior? I don't think so. 70 cri 4000k will be king if 400-700 nm photons is all that counts .

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Plants do the down conversion for all wavelengths less than 700nm to condition the photons for photosynthesis. By doing most of the conversion of a blue photon to a red one with the led phosphor this helps improve photosynthetic efficiency as providing higher wavelength light requires less conversion to be done by the plant.

Currently I still think we are better off with the lower CCT at whatever CRI puts out the most photons over 600nm. Put out as many photons as possible and let the plant sort it out.

By the way, that conversion results in heat being generated as waste, both in the plant and in the led. Just like we do with led, the plant has to spend resources for thermal management. Anything we can do to help facilitate or improve plant functions will allow the plant to spend more photosynthetic output on growth. Pre-conditioning light to the optimal wavelength seems to follow that principle.

Shugglet said:

Does an HPS light not fall within the curve or something? What are you getting at?

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It does but look at the response ...according to Mc Crees data plants are more receptive/can make better use of red correct?

What does the real world say?

Hps especially the old ones were pretty much only green and yellow yet you can grow killer bud under them.

How many others have been able to do the same for canna under heavily red bias spectrums???

Is that clear enough as to why the data is flawed and why spectrum is important ...or should I go on lol?

Shugglet said:

I dont think it was developed with any of that even in mind. I wouldnt knock it for not being able to answer things it was never intended to answer.

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You are correct, maybe my criticism of the McCree experiment is on the harsh side, after all he did pave the way so he definitely deserve recognition for that fact.

But my gripe is when people start using his data like it is the definitive word on all things grow wise ...I have explained in my previous posts why it is crazy to use his data as a baseline and I have done my own tests which prove his data is not the be all and end all.

On that note respect to Keith McCree but things have moved on significantly since his era!