# CRI? Does it really matter?



## Seattle_Aquarist (Jun 15, 2008)

Hi All,

I have noted some interest in the color rendering index (CRI) lately in a few posts. The question comes to mind.....why? The CRI of a light source has no effect on plant growth only upon how I view my tanks. The higher the CRI the more 'true' the color would be compared to how it would look on a sunny bright day. However that may not be the look I like!

Cara Wade from BuildMyLED did a talk at GSAS here in Seattle in October, 2015. She explained it this way, that if we were to take a picture at high noon on a sunny day the picture would have a high CRI but the colors and contrast overly strong and harsh. Most people actually do not prefer a "high CRI" look but instead seem to prefer a 'softer' somewhat less intense appearance. I guess that is why many of 'adjust' our photos with Photoshop or other software to 'improve' the way they look to us.

I know for a fact that 6700K seems to have too much 'yellow' for me and I prefer lighting in the 8800K - 9350K range. Yes, the colors aren't as 'warm' but the blues and reds seem to 'pop' better with the higher K lighting. I guess that beauty truly is in the eye of the beholder.


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## Bunsen Honeydew (Feb 21, 2017)

Seattle_Aquarist said:


> Hi All,
> 
> I have noted some interest in the color rendering index (CRI) lately in a few posts. The question comes to mind.....why? The CRI of a light source has no effect on plant growth only upon how I view my tanks. The higher the CRI the more 'true' the color would be compared to how it would look on a sunny bright day. However that may not be the look I like!
> 
> ...


Given that it is subjective, one can only say that it matters only if it matters.😀

That said, I think that my Beamswork looks great, so what do I know?

Sent from my Nexus 6 using Tapatalk


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## jeffkrol (Jun 5, 2013)

> Cara Wade from BuildMyLED did a talk at GSAS here in Seattle in October, 2015. She explained it this way, that if we were to take a picture at high noon on a sunny day the picture would have a high CRI but the colors and contrast overly strong and harsh.


..Contrast has nothing to do w/ CRI really..
Strong has to do w/ overall intensity.. Can't "dim" the 6500k sun really.. 

All colors ar represented equally w/ a "tilt" to blues










10,000k sun
SIMULATION DATA
----------------------------------------
Luminous flux : 99,999 lm
Radiant flux : 505,338 mW
PPF : 1,902 umol/s
TCP : 9900 K
CRI : 81
λp : 453 nm
Color : #A5D0FF

I can sort of get where she is coming from but it doesn't "exactly " apply..
http://www.mdavid.com.au/photography/washedout.shtml
http://www.mdavid.com.au/photography/harshlight.shtml

applies to photography more than anything else..

This is kind of fun..
http://nofilmschool.com/2016/04/led-lights-comparison-review-color-shootout



> Well what can be said about the sun? It is bright and perfect. Notice how dense the spectrogram on the meter is. Nearly every wavelength is fully saturated. This is what the Daylight LED's should mimic.


https://youtu.be/JqnrLv36Lp4


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## Maryland Guppy (Dec 6, 2014)

Seattle_Aquarist said:


> The question comes to mind.....why?
> The CRI of a light source has no effect on plant growth only upon how I view my tanks.
> 
> I know for a fact that 6700K seems to have too much 'yellow' for me and I prefer lighting in the 8800K - 9350K range. Yes, the colors aren't as 'warm' but the blues and reds seem to 'pop' better with the higher K lighting.
> ...


I have never considered the CRI of any of my LED purchases.
I'm liking the higher K rating too.

I began using full spectrum weed grower LED's and mixing them with 15K 1:1
This cuts the pink/purple look but seems to grow plants better.

It's all in the eye of the beholder.:grin2:
I don't really like the final "K" look of my lights, it could be higher.


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## jeffkrol (Jun 5, 2013)

It is, admittedly, more of an obsession... 

K and CRI aren't really related..that was another point.
https://www.marinedepot.com/175_Wat...ght_Bulbs-Iwasaki-MB4711-FILTBUMHSEHS-vi.html


nor does CRI nor K have anything to do w/ plant growth. Thought that was somewhat of a given.. 
some of your issues are probably more CRI related tha K temp related..

Thought at one point you stuck a cyan in the mix..


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## Seattle_Aquarist (Jun 15, 2008)

Hi @jeffkrol,

Cara Wade covered a lot of the "common lighting myths" in her talk, one had to do with spectrum, light intensity (PPFD) and plant growth. She cited a study done by professor Dr. Bruce Bugbee from Utah State University where all plants grew exactly the same amount (+/-) no matter the light spectrum they were grown in if they had the same PPFD; not at all what I expected!


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## jeffkrol (Jun 5, 2013)

> nor does CRI nor K have anything to do w/ plant growth.


You sort of miss one subtle point (well 2)
All have "some" blue so no pure colors.
And I may miss some of it but one needs "long term" effects. Or like root development, mass, pigments, flavenoids, vitamins, flowering, disease resistance ect..
Not dissing it.. just "pushing" it..


Again K nor CRI have anything to do w/ plant growth..

Few would want "ugly" lighting just because plants don't care.. 



> Dr. Bugbee presented the following quote by Dr. Frits Went, author of the book “The experimental control of plant growth”: “Photosynthesis does not control plant growth, plant growth controls photosynthesis.” Other speakers agreed with this quote, and it became one of the discussion points throughout the conference. We often think of photosynthesis as the main factor driving plant growth. However, photosynthesis by itself it is not a good indicator of overall plant growth. Environmental factors such as light intensity and quality alter plant development and morphology, which then change the plant’s capacity to carry out photosynthesis.
> 
> For example, in the last article I wrote (“Luminous possibilities,” accessible here: bit.ly/1UlfPhS), I showed how cucumber seedlings’ net photosynthetic rate increased with the increase of blue photon flux. However, the plant’s dry mass decreased with the increase of blue photon flux. In this particular example, plant leaf area was affected by the light quality, which then affected the plant’s capacity to intercept light. Here, the growth rate was better predicted by the relationship of leaf area and photosynthesis, and not by photosynthesis alone.
> 
> ...


http://www.greenhousemag.com/article/the-latest-on-lighting/


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## Seattle_Aquarist (Jun 15, 2008)

jeffkrol said:


> The latest on lighting - Greenhouse Management


Hi jeffkrol,

Thanks for the link.


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## jeffkrol (Jun 5, 2013)

Seattle_Aquarist said:


> Hi jeffkrol,
> 
> Thanks for the link.


I'd appreciate a better summary of this article if you have access...



> Consequently, horticulture crops are now often exposed to light climates that they would never have experienced in nature. Applying lighting to plants beyond their natural comfort zone may also results in unexpected negative effects. This hampers the development of optimal lighting strategies in horticulture. In this paper, two examples of such negative effects on leaf photosynthesis are presented, aiming to induce a discussion on how genetic and physiological knowledge from natural systems may help to develop new lighting strategies for horticultural production in greenhouses and plant factories.


Plant growth control by light spectrum

Maybe CRI matters.. "snicker"..


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