Fluorescent Lighting and CRI - How important is it?

[ScrubNinja]

Colour Rendering Index on wikipedia.

I've read advice on either side of the scale. It seems to me like a low CRI would be desirable - The extra coatings used to obtain that CRI are blocking out more light, and that's expressed in the lower lumen figure. So is it as simple as that? This guy seems pretty keen on high CRI. I don't completely understand his reasoning why but check it out anyway.

 

[superpedro]

Colour Rendering Index on wikipedia.

I've read advice on either side of the scale. It seems to me like a low CRI would be desirable - The extra coatings used to obtain that CRI are blocking out more light, and that's expressed in the lower lumen figure. So is it as simple as that? This guy seems pretty keen on high CRI. I don't completely understand his reasoning why but check it out anyway.

I don't understand him either.
With a high CRI bulb you are assured a certain amount of red and blue, and you won't find any bulbs that totally sucks, but the better blue/red spikes are found among cheaper CRI 8 and below. I know you risk buying "greenish" bulbs too when choosing low CRI bulbs. That is more likely to happen if you search for skyhigh lumen output plus a low CRI, since green is favored by the lumen scale.

Plants are green. Since an eye is nothing else than a receptor for light, what I see as different colors is really allot of unique materials reflecting light at different wavelengths. Colors not reflected are converted into work or heat.(a way to measure light uptake is to measure the reflection and surface temp of a leaf)
Goes without saying plants have no use for white or natural light, when an pretty equal amount of all wavelengths RG&B is needed to make it.
Blue-Red-FRed.. Thats it.

Peace.

 

[maryjohn]

Is this going to lead to a guide of which bulbs to buy?

Hey everyone, pedro's doing a guide! Thanks Pedro!

 

[ScrubNinja]

Goes without saying plants have no use for white or natural light, when an pretty equal amount of all wavelengths RG&B is needed to make it.
Blue-Red-FRed.. Thats it.

Thanks man. Could you please elaborate on this bit? I'm not sure what you meant. Are you saying blue, red, and far red are all that's needed to grow a plant?

I agree Mj, pretty nice of Pedro to volunteer to write a guide up. Let me know when it's finished please

 

[superpedro]

LoL guys.

Thanks man. Could you please elaborate on this bit? I'm not sure what you meant. Are you saying blue, red, and far red are all that's needed to grow a plant?

I agree Mj, pretty nice of Pedro to volunteer to write a guide up. Let me know when it's finished please

I meant white light/ High CRI natural light, is an optical illusion consisting of an equal amount of red green and blue, meaning any application of white light together with red and blues is the same as arguing green is a good color grow light.
If you apply only blue, red and far red at the optimal nm in the correct ratio, your plants will be able convert the highest possibe amount of light into work.
Thats why plants under perfect lighting seems almost black in leaf color because no light is reflected.

I can't make a guide really. Like scrubs pointed out in an earlier thread, bulb manufactures rarely gives enough information if any at all.
Ever noticed that different strains have different leaf colors? They are all adjusted to a slightly different light uptake.
A plant changes its need for blue/red through out the flowering too, some plants create pigments (anthocyanins) to control the uptake of light. When plants turns red it reflects the red spectrum, it does so to block out energy it can't use.

The best I can do is to give a few advices I've already mentioned before.
1 High CRI bulbs kick ass for photography in your cap, as a grow light because of what the CRI scale really means, they can't be better than average.
2 When you buy low CRI bulbs without spec graphs, don't go for the highest lumen output, or you might end up with a greenish spectrum!
3 Check out your local aquarium store for low CRI plant bulbs with pinkish color, they cost a bit more but often come with most data as well.
And good luck hunting

 

[fatigues]

CRI is ultimtely a measure intended to be used by interior designers to assess how much like incandescant light a particular light fixture's light is.

It's not intended as a number to be used by horticulturalists in planning the utility of a particular SPD thrown off by a given lamp.

While green light is not the most important light used in the production of chlorophyll A and B, it IS used by the plant to make carotenoids. The belief that green light is unimportant in plant growth is, therefore, fundamentally incorrect.

Moreover, the plants DO use green light to make chlorophyll as well -- and it is a myth that they do not. Here's the quote

A widespread misconception states that leaves reflect all green light and do not use green light in photosynthesis. Leaves often absorb more than 50% of the green light and use it efficiently in photosynthesis.8,22 The origin of this misconception is probably the chlorophyll absorption spectrum in textbooks. The chlorophyll absorption spectrum is a graph of light absorption versus light color. It shows that chlorophyll absorbs much red and blue light but little green light. However, accessory pigments absorb green light and pass that energy on to chlorophyll.

See the discussion here for more.

As for CRI - if it's above 80, in most cases you'll be fine. Most of the floursecents we consider using here on ICM are in the mid to high 80s. There are some in the low 90s - but I don't think that the extra cost for being 90+ is especially important Scrub.

I answered "important", with an 80+ CRI being the threshold for "high" CRI. If you consider 90+ being the threshold for "high CRI", then no, it's not important. 80+ and you are good to go.

 

[superpedro]

Not talking what they can use, but what they can make the most use of.

While green light is not used in the production of chlorophyll A and B, it IS used by the plant to make carotenoids. The belief that green light is unimportant in plant growth is, therefore, fundamentally incorrect

All professional studies I've seen says the carotenoids can use up plenty enough of the blue light around 450nm.
That is also why the professional. LED setups for plant studies, in vitro and nurseries runs with only those 3 colors and focuses on chlorophyll A and B.
http://www.lighting.philips.com/in_...=gb_en&parent=1&id=in_en_applications&lang=en

 

[high4free]

I found a chart for Osram pll's and the ones with CRI 90+ (Lumilux De Luxe) have a better spectral output, there aren't any spikes and there is more available light in the peak wavelenghts although they have less lumens.

scroll to see the charts

 

[fatigues]

All professional studies I've seen says the carotenoids can use up plenty enough of the blue light around 450nm.

You should read those papers in the original link Pedro. Some of that research is new and published only this year. There are a lot more articles on the subject in journals that are not accessible online without an academic research id/password. Though from the look of your pics "lab setup" that my husband has shown me, it may be that you already have the necessary account access?

That is also why the professional. LED setups for plant studies, in vitro and nurseries runs with only those 3 colors and focuses on chlorophyll A and B.
http://www.lighting.philips.com/in_...=gb_en&parent=1&id=in_en_applications&lang=en

You'll forgive me if I remain unconvinced by any company's "professional LED" setups. Engineers are not botanists -- and not all botanists agree on this point.

I've taught botany in the past, though that is not my area of research. There is a botanist in my faculty whose research is specifically on this subject. He is also convinced that green light plays an important role in plant development which has been downplayed over the years.

I try to keep an open mind on these matters. Perhaps you should as well?

 

[messn'n'gommin']

You don't even have to register to access the database here.
http://www.plantphysiol.org/contents-by-date.0.shtml
Archives of, “Plant Physiology,” Published by the American Society of Plant Biologists

You may have to buy some of the articles here, but a lot of them are free.
http://www.plantcell.org/contents-by-date.0.shtml
Archives of, “The Plant Cell,” sister site of, “Plant Physiology,”

http://www.beckleyfoundation.org/bib/doc/crl/Cannabis_the_plant/Mahlberg_1983.pdf
Effect of Light Quality on Cannabinoid Content of Cannabaceae

http://www.plantphysiol.org/content/vol133/issue4/
UV-B Mediated Responses in Plants
BL Signaling Through the Cryptochromes and Phototropins
The Red Side of Photomorphogenesis

http://www.plantphysiol.org/cgi/content/full/125/1/85
“Photoreceptors in Plant Photomorphogenesis to Date,”

http://www.plantcell.org/cgi/conten...=&searchid=1&FIRSTINDEX=10&resourcetype=HWCIT
The Phototropin Family of Photoreceptors

If you are anything like me, some of them may as well be written in greek, but that doesn't mean you can't grasp the gist of what the author has to say.

Namaste, mess

 

[superpedro]

You should read those papers in the original link Pedro. Some of that research is new and published only this year. There are a lot more articles on the subject in journals that are not accessible online without an academic research id/password. Though from the look of your pics "lab setup" that my husband has shown me, it may be that you already have the necessary account access?

You'll forgive me if I remain unconvinced by any company's "professional LED" setups. Engineers are not botanists -- and not all botanists agree on this point.

I've taught botany in the past, though that is not my area of research. There is a botanist in my faculty whose research is specifically on this subject. He is also convinced that green light plays an important role in plant development which has been downplayed over the years.

I try to keep an open mind on these matters. Perhaps you should as well?

Hey thanks. Guess there is enough solid theory out there for us to disagree about I am trying to keep an open mind, otherwise I never learn new stuff. At the same time I got to be skeptical, otherwise I learn all the wrong things.

Yes, we got a free pass to search the scientific databases through the university. But when at home, like now, I'm only able to read the abstract.

An experiment with green LED's in lettuce with good results is impressive, and so is the source, but at the same time I'm sure you agree, when dealing with groundbreaking hypotheses, there is a long road before one or a few studies becomes a general rule you can apply to all plants?

I'm very critical about my sources, that goes with the lights too.
I am a gardener while my wife is the biologist, I read about every new led test results in the weekly journal (It's all about saving energy these days). I don't feel bad about forming my advise based on what I've read about plant light and seen grown under B-R-fR LED's
Those lights has been co-developed and tested by Philip's and DTU (Danish technical university) in collaboration with something called Agro tech, a Danish independent department that supports the professional gardeners in research.
It's no random internet based grow light. Found an mention (in english) of Philip's and the collaboration at the bottom of this page:http://en.cop15.dk/climate+consortium/news/view+news?newsid=2458
I'm not saying that it guarantees new research wont prove that it could be build improved.

And thanks, I will keep and eye out for any more news from "the green department."

Cheers.

Back on topic, How can people think a cfl with a high CRI is related to good plant growth, when the superior hps has a very low CRI, and a LED growlamp (Even if you mix in a few whatever nm LED's) has to be an even lower combined CRI than the hps?

 

[maryjohn]

holy cow that was awesome!

so... when is the fatigues/pedro guide coming out?

 

[fatigues]

An experiment with green LED's in lettuce with good results is impressive, and so is the source, but at the same time I'm sure you agree, when dealing with groundbreaking hypotheses, there is a long road before one or a few studies becomes a general rule you can apply to all plants?

I completely agree. My comment was on the fact that there is a belief that green light does not play an important role in plant development. This is fundamentally wrong; however, that does not mean that the concentration on blue and red spectrums is ill-conceived.

I'm very critical about my sources, that goes with the lights too.

I as well. I'm a scientist. I place no reliance upon touch-feely anecdotes or New-Agey theories of any kind. You won't see me posting (or reading) in any chanting threads

I am a gardener while my wife is the biologist, I read about every new led test results in the weekly journal (It's all about saving energy these days). I don't feel bad about forming my advise based on what I've read about plant light and seen grown under B-R-fR LED's

Then I have something in common with both you and your wife. I'm a biologist and the actual garderner in our house. We both post under this account (he is a far more active poster than I). If you have read my husband's posts elsewhere on ICM, you can well guess what he does for a living.

Consequently, he grows arguments well (and bank accounts too, I suppose). His hobby on the tech design side of putting together toys to grow plants is mostly harmless. But when it comes to actually growing plants? I try to keep him at a safe distance away from the plants - both indoors and out - so he doesn't kill them.

He'll probably read this and edit it to try to censor the truth! But it's true just the same

[EDIT: A lump of coal for you this year sweetie, to match my "black" thumb.]

 

[superpedro]

lol, My wife knows answers to most of my questions, but she would never be allowed to water my plants

Boys just needs to blow somthing up now and then..

 

[messn'n'gommin']

Colour Rendering Index on wikipedia.

I've read advice on either side of the scale. It seems to me like a low CRI would be desirable - The extra coatings used to obtain that CRI are blocking out more light, and that's expressed in the lower lumen figure. So is it as simple as that? This guy seems pretty keen on high CRI. I don't completely understand his reasoning why but check it out anyway.

Sir, please do not misunderstand, I do not mean to insult your intelligence, but manufacturers make their bulbs, primarily, to illuminate the dark for the human eye and sell them as such, with little consideration, if any, for the photosynthetic process. CRI is a relative measure of the human eye to distinguish between different colors in sunlight. So, by itself, CRI is a poor gauge of measuring a lamps effectiveness for photosynthesis as well as a lamps measure (each taken separately) of lumens, fc's, etc. However, all of them taken together, gives growers a better measure (short of an SPD chart) he/she needs to gauge that effectiveness and is the only real resource the manufacturer provides for their product. So, by itself, is CRI important? Not really. But, until manufacturers start adding the SPD (and/or PPFD, etc.) on the box neither is it (nor lumens, fc’s, etc) unimportant. I think the important thing is to keep it in perspective and consider other measures as well, to best determine what a particular lamp can or cannot do.



Namaste, mess

 

[superpedro]

One thing you got to watch out for is the use of a relative scale. CRI 9 bulbs looks appealing at first glance, but the diagrams doesn't compare that easy.
You got to trust the physics involved in making an improved spectrum(for humans), adding extra compounds to the bulbs to change some wavelengths, will in most cases lead to a drop in the total light output.
I just remembered and old physics experiment, you can compare the light output of bulb, by submerging it in water by use of an enclosed tube. By measuring the terminal temperature of the water, and calculating the calories used to reach it, you can find the output of visual light.

High CRI small spikes full spec, Low CRI high spikes, thats the one thing we can all agree on?

Pic's of CRI 1 bulbs (Hard to find)

@fatigues

I have arranged for a talk with one of the those involved in the mentioned LED field test in January.
I'll ask him about the choice of only those 3 nm's.
Anyway. Guess you know about shade leafs? Some plants, especially big trees use their upper leafs to collect the blue and green. Further down the canopy, leaves receive only some green light and IR radiation, those leaves have extra pigments for utilizing the last energy in the shade. Is that what the early quote was about?

Lettuce grows all new leafs the shade of the old, this could make it a plant with extreme adaptations to wards getting some energy to the most shaded leafs. Unlike cannabis, lettuce would rot away if it moved nutrients and rejected a leaf because of shade. Too me I can see some logic to lettuce having a unique evolutionary "reason" for development of ways to use all radiation energy.
Cannabis IMO doesn't show any signs of keeping the leafs that only receives light filtered through a canopy (when the scrog screen closes, the lower leafs drop very fast). No fast growing plants with comparable stature does - as far as I know. It seems easier to move the nutes to fresh new growth instead.
The lettuce results really got me thinking I'd admit to that, but have you found something about better comparable plants and green light? I would like to know as much as possible before I get to question those who know more. They have been running field tests for 4 years now, with those institutions involved I expect some know how on the subject.

cheers.

 

[ScrubNinja]

No problem messn, thanks for adding. Thanks everybody - I just wanted to say that since I have nothing to really add at this point. Please carry on.

Oh wait a sec, I read a post where knna explained

Main general studies about this topic were performed by McCree and Inada in the 70's of last century. Their results have been repeated many times for specific plant species, so their results are widely accepted as valid. Both performed the studies by irradiating the plants with narrow bandwiths of light (2nm) and measuring the photosynthesis (by O2/CO2 changes).

How did they get lights capable of this back in the 70s? LED?

Pedro, you know so much, including co2...how useful is this way of measurement in real terms of ending up with a great plant (ie: budz)? Wouldn't measuring via co2 only indicate which plant was growing the most leaf? If so, I know there's gonna be a correlation of some kind between leaf, and buds, but nevertheless, it is only leaf (if my assumption is correct?)

 

[superpedro]

Thanks, I love this forum where people seems able to disagree in good manor
Filters perhaps?

You would be measuring all growth. The primary uptake doesn't have to happen where or when the new cells are formed, the carbon is transported or stored as glucose. If your plants doesn't get to cold, they grow at night too.

 

[maryjohn]

I though heading lettuce was a cultigen?

 

[superpedro]

I though heading lettuce was a cultigen?

It's been around for a while http://www.hort.purdue.edu/rhodcv/hort410/lettuc/le00001.htm