Why CRI is Important, or How to Make LED Lighting Look Great

joelespinoza · 07/22/2012, 08:13 AM

"CRI = Color Rendering Index (CRI) would measure the ability of a light source to accurately render all frequencies of its color spectrum.... It is rated on a scale from 1-100. The lower the CRI rating, the less accurately colors will be reproduced.... An acceptable Color Rendering Index level for professional imaging is considered to be 90 or above."

Taken from - http://lowel.com/edu/color_temperatu...mystified.html

Switch gears for a moment and forget tank lighting, pretend you are an aspiring photographer and look at your tank like it is a model at a photoshoot. You just did some shots outside under natural lighting and the model looked great, then you go inside and to get some shots, and this time you want that same bright, natural look but toned towards blue.

So you setup your cool white, low CRI lighting, add the blue suppliments and you bring in your model..... and she looks like a a ghoul. She is completely washed out, reds, oranges, greens, and yellows are gone, and there is simply no color definition, her color looks flat and lifeless.... So you break out the narrow band red and green supplimental lighting and adjust and adjust and adjust...

But no matter what you do there is no real depth to her color, you just get bright peaks in the areas you added supplimental colors, without the fine gradients you get under natural sunlight, so whats wrong?

So you seek out an experienced professional photographer and tell him your problem and ask him how to fix it, and he asks to see your lighting, so you break out the specs:

•8x Cree XP-G Cool White LEDs run at 5w each (~70 CRI average)
•8x Cree XP-E Blue LEDs run at 3w each (~470-480nm average)
•10x Cree XP-E Royal Blue LEDs run at 3w each (450-460nm average)
•4x Cree XP-E Green LEDs run at 3w each (◦520-535nm average)
•4x Osram Oslon SSL Hyper Red LEDs run at 3w each (660nn)

Now what do you think the first thing that experienced photographer will point out? Your base white lighting is completely wrong, why did you get the lowest CRI white lighting you can find? By definition it doesnt accurately represent colors.... Any professional wanting realistic colors is going to start with 90+ CRI white light, then tone it from there, not try to create high CRI light from scratch themselves at the shoot.

This makes perfect sense right? No photographer would try to recreate the wheel. Why do we do that to ourselves when doing LED lighting for aquariums?

For some silly reason someone started making LEDs for aquariums with low CRI cool white bulbs and it caught on (probably all that was available at the time). Then people wanted colors back that they used to have, because full spectrum lighting is available with both metal halides and T5, so they started adding color outside cool white and royal blue, striving to have all the colors show up accurately, then manufacturers (like ecotech) emulated this, and started selling fixtures that used this same idea, one that was flawed to begin with.

So step away from that hodge-podge idea for a moment and consider what you would get if you started with high CRI warm whites, you might get something like this, where colors look natural and have both definition and gradients:

That is actually a picture from SushiGirl of LED sump lighting.

Now, what if you want some blue tone added to the white light? Here is a tank shot of a freshwater LED setup tank that I took, the clarity is not as good as SushiGirls but the color is accurate to my eye, it actually does have that nice purpleish glow in person too, thats not just an effect of the camera:

So does anyone notice a difference in these 2 pictures from the standard flat washed out looking 1:1 Cool white LED setups?

tomservo · 07/22/2012, 09:39 AM

This is why I based my reef lights around citizen multichip arrays.. Not only are they extremely good value, they are 85 CRI. I paid $16 each for the 64w 4000k versions I used. Surrounded them with a bunch (26-30) of 4w blues and some 420's. The results are amazing, I should take some pics of my friend's tank next time I visit. Pics of my tank are less than helpful, as I don't yet have any corals, just a maxi mini anemone.

The lights I put over my friend's tank replaced eshine 60w units, with a marked improvement in color of corals and fish.

The efficiency is right up there with any leading high CRI emitter, 75-85 lumens/watt.

I just noticed looking up specs that they now have a 90 CRI 4000k emitter.

product info: http://ce.citizen.co.jp/lighting_led...cts/index.html
I used the CLL234A 5000k 85 CRI for my cichlid tank, and for my friend's fuge. CLL030-1212 4000k 85 CRI over the reefs.
avnet has many of the emitters in stock (USA distributor) and the ones they don't, there's no minimum qty to special order!

The real problem with the low CRI cool whites is the strong emphasis on the green/yellow spectra that our eyes are so sensitive to, which makes for crazy good lumen/watt ratings. You're not necessarily getting any more actual output power than the high CRI types, our eyes are just more sensitive to green/yellow.

nyquist · 07/22/2012, 10:27 AM

Just keep in mind that CRI is all about rendering colors as they appear in natural sunlight, defined by the spectral distribution of the sun at the earth's surface.

High CRI lighting is good for accurately lighting extremely shallow ocean organisms (many algae, mangroves, shallow water sea grasses, etc). However, A reef sitting even just 10 meters below the surface of the ocean is not sitting in the typical spectral distribution from natural light, as water filters light passing through it. Red light has an attenuation coefficient nearly two orders of magnitude higher than blue or violet in water, thus accurately lighting a typical reef does not involve much red (or yellow or yellow-green).

So a high CRI light source may look pretty and show you how the corals would look out of water, but it is often further from the natural lighting available to corals in the wild when compared to the blue and purple tinted lighting many LED fixtures provide.

joelespinoza · 07/22/2012, 10:43 AM

Quote:

Originally Posted by nyquist

So a high CRI light source may look pretty and show you how the corals would look out of water, but it is often further from the natural lighting available to corals in the wild when compared to the blue and purple tinted lighting many LED fixtures provide.

I am not arguing that most wild corals have to adapt to live in our tanks, no matter what conditions we keep the tanks at. There is no possible way to exactly mimic the natural conditions our corals evolved in, even if all your corals from a single location and all chosen from the exact same depth, which very few people do.

This is a post about astetics of reef lighting, which is a big part of the enjoyment of reefkeeping and why LED lighting often looks so lackluster compared to MH or T5 lighting.

As a side point: In the VAST majority of cases, visibly "Purple" light with LEDs comes from adding red to blue lighting (either as pure red, or white with warm tones). Royal Blues alone do not usually look purple, and violet light is drowned out so quickly, you would need a fixture that was over half violet to make a noticable difference.

sirreal63 · 07/22/2012, 11:34 AM

Quote:

Originally Posted by nyquist

Just keep in mind that CRI is all about rendering colors as they appear in natural sunlight, defined by the spectral distribution of the sun at the earth's surface.

High CRI lighting is good for accurately lighting extremely shallow ocean organisms (many algae, mangroves, shallow water sea grasses, etc). However, A reef sitting even just 10 meters below the surface of the ocean is not sitting in the typical spectral distribution from natural light, as water filters light passing through it. Red light has an attenuation coefficient nearly two orders of magnitude higher than blue or violet in water, thus accurately lighting a typical reef does not involve much red (or yellow or yellow-green).

So a high CRI light source may look pretty and show you how the corals would look out of water, but it is often further from the natural lighting available to corals in the wild when compared to the blue and purple tinted lighting many LED fixtures provide.

Also note that not all reefs are at that 30 meter mark, many are much much less and a lot are exposed to the air during low tide. The colors of a shallow water reef are closer to the appearance we strive for in our tanks because that 90 foot deep reef looks blue and dull until lit by high powered flash from a camera. The point is that for our tanks the high CRI is an important feature of good lighting, unless you are going for that dull blue look.

.

nyquist · 07/22/2012, 12:40 PM

Quote:

Originally Posted by sirreal63

Also note that not all reefs are at that 30 meter mark, many are much much less and a lot are exposed to the air during low tide. The colors of a shallow water reef are closer to the appearance we strive for in our tanks because that 90 foot deep reef looks blue and dull until lit by high powered flash from a camera. The point is that for our tanks the high CRI is an important feature of good lighting, unless you are going for that dull blue look.

but I didn't say 30m, I said 10m :P

and I believe most thriving, natural reefs exist between 10m and 25m or so; though like you said, many reefs are exposed or nearly exposed during low tides, but I'm not sure how much in a hobbyist's aquarium is from that environment

either way, I've just always liked light just on the natural blue side of a well-rounded full spectrum white, so I guess it's still more of satisfying your preference than anything

sirreal63 · 07/22/2012, 02:04 PM

Sorry about that, bad drugs this morning, 30 ft is deep enough to give that overly blue look, and our tanks are really more closely related to a shallow reef environment with a more full spectrum of light. The wonderful thing about most of the corals in our tanks is they come from the full range of reef depths, we hopefully want to show our tanks in the best light so our lighting should be up to the task. This really hasn't been much of an issue with more traditional lighting but is with the more narrow lighting of most LEDs. I understand Joel's thread to mean just that, pay attention to the CRI of the lighting, it does make a difference.

As far as depth, it varies greatly as well as the conditions of the reef. I don't think it is possible to say that one is healthier than the other. There are just too many variables,shallower reefs get more full spectrum, higher Par and more turbulent flow, etc etc. I prefer the Radium look but for growth it is hard to beat the 10k bulbs, it is just a preference and that is ok, it's what keeps everyone's tank from looking the same. :-)

nyquist · 07/22/2012, 02:31 PM

true, reefs would be a little boring if everyone chose the same critters to display under the exact same lighting conditions

joelespinoza · 07/22/2012, 02:33 PM

Quote:

Originally Posted by nyquist

either way, I've just always liked light just on the natural blue side of a well-rounded full spectrum white, so I guess it's still more of satisfying your preference than anything

This thread is about opening up the possibilities of LEDs outside what is commonly done, and how to simply provide a depth of color that is usually lacking from LED builds.

Obviously you can build a light fixture that more closely mimics deep water reefs. That light color would have 90%+ of its light generated between 470-495nm. If you want to make a turquoise-blue light that makes corals look flat and colorless, its not difficult to do. The light would be about this color:

Most people think that looks ugly.

LEDs open a world of possibilities, this is just a different option that I feel many people who currently feel LEDs are lacking should look into.

tomservo · 07/22/2012, 11:04 PM

Quote:

Originally Posted by nyquist

Just keep in mind that CRI is all about rendering colors as they appear in natural sunlight, defined by the spectral distribution of the sun at the earth's surface.

Just a small correction; CRI is based on incandescent lights; a halogen bulb should have a CRI of 100.

That said, the importance of high CRI is more to do with the spectra that make up the light; for example you can get a 67 CRI 5000k citizen emitter - little red and much yellow/green, very high lumens/watt. They also make a 85 CRI 5000k; less green/yellow, much more pronounced orange/red/deep red spectra as well as increased cyan.

I'm not trying to match some ideal, I just want my inhabitants to look good in a reasonable way.. Seems to me there's less fuss in having enough red in my white emitter vs attempting to add it after the fact. (and getting horrible disco shadows).

I tried to get citizen to make me a batch of 10000k emitters with their phosphor blend.. no dice! They also won't make emitters with no phosphor(RB).

Pny · 07/23/2012, 05:22 AM

I'm afraid CRI is more or less useless for measuring LED output because of the way the CRI value is calculated...

"The color rendering index (CRI) has been used to compare fluorescent and
HID lamps for over 40 years, but the International Commission on Illumination (CIE) does not recommend its use with white light LEDs."

Taken from:
http://cool.conservation-us.org/byor...ring_index.pdf

joelespinoza · 07/23/2012, 06:58 AM

Quote:

Originally Posted by Pny

I'm afraid CRI is more or less useless for measuring LED output because of the way the CRI value is calculated...

"The color rendering index (CRI) has been used to compare fluorescent and
HID lamps for over 40 years, but the International Commission on Illumination (CIE) does not recommend its use with white light LEDs."

Taken from:
http://cool.conservation-us.org/byor...ring_index.pdf

You are getting caught up in semantics, I am not claiming that out of 2 closely rated LEDs, one is better then the other. I am saying that we should start using LEDs that are made to accurately represent color, rather then ones that are specifically made NOT to accurately represent color. The standard white LED is a cool white, and they are as bad as it gets.

Here is the "Standard" white LED used in high end builds that is rated at around 70 CRI:

http://www.rapidled.com/cree-xp-g-r5-cool-white-led/

Here is the one that rated at around 95 CRI:
http://shop.stevesleds.com/Philips-L...-warm-2700.htm

Go get them both, plug them in and then get back to me about which represents color more accurately. The difference is night and day.

Quote:

Originally Posted by tomservo

The real problem with the low CRI cool whites is the strong emphasis on the green/yellow spectra that our eyes are so sensitive to, which makes for crazy good lumen/watt ratings. You're not necessarily getting any more actual output power than the high CRI types, our eyes are just more sensitive to green/yellow.

You make an excellent point here, I am sure people still look at LEDs and go ohh this white has 75 lumens/watt but that one has 100 lumens/watt! Its still hard to get over the idea that more light is not always better with LEDs, and that more lumens does not necessarily mean more PAR/PUR. But in the end, the complaints over lack of light are few with LEDs, whereas the the complaints over lack of color are many.

nyquist · 07/23/2012, 08:51 AM

Quote:

Originally Posted by tomservo

Just a small correction; CRI is based on incandescent lights

well actually, that is not correct either :P
CRI is not based on incandescent lights, it is based on blackbody radiation, and how closely a light source matches the radiation of a blackbody source. It just so happens that the sun is a convenient example of a blackbody radiator

joelespinoza · 07/23/2012, 12:15 PM

The specific definition here is not important.

The basic definition is simply that higher CRI rating means colors will be rendered more "accurately" to us.

IE the color of the objects put under 100 CRI lights will look approximately the same to us as if they were lit by the sun, although the color of the light itself may or may not be the same color.

This is something greatly lacking in cool white LED builds.

bhazard451 · 07/23/2012, 12:46 PM

No one has really nailed down a perfect ratio of CW:NW:WW yet. I used 6:3:3 to 24 royal blues + 4 violets + 2 cyan + 2 blue + 2 green + 2 red in a 48 led fixture, and I am pleased with the results. It resulted in a 12-14k look, which I enjoy compared to something more blue.

I'm still tinkering with it, but some colors like orange really pop. I don't think anything on the market uses a ratio like this.

joelespinoza · 07/23/2012, 01:20 PM

I am actually not sure why you would want to use any cool whites at all. Even my first neutral white setup is lackluster compared to the later Luxeon 2700k warm whites I have done.... I think the perfect white ratio is all high CRI whites.

As far as supplimetal colors go, I dont think there is any point really. Violets are nice, but it takes a TON to make any noticable difference in a fixture. Reds, greens, blues and cyan just arnt required if you have whites that actually render colors accurately...

bhazard451 · 07/23/2012, 02:17 PM

Too many warm whites are extremely yellow, and would require that much more blue to balance it out. Running just the white channel even with 6CW mixed in on mine looks horrid, around 6-8k.

I also disagree with needing a lot of violets. The difference is very noticeable with only 4 of them. Although they may look visually dim, there is an added fluorescence that actinic light provides compared to not having them. Same concept as adding 420nm actinic T5 supplementation.

07/22/2012, 08:13 AM	#1
joelespinoza Moved On Join Date: Dec 2011 Location: Galveston Posts: 417	Why CRI is Important, or How to Make LED Lighting Look Great "CRI = Color Rendering Index (CRI) would measure the ability of a light source to accurately render all frequencies of its color spectrum.... It is rated on a scale from 1-100. The lower the CRI rating, the less accurately colors will be reproduced.... An acceptable Color Rendering Index level for professional imaging is considered to be 90 or above." Taken from - http://lowel.com/edu/color_temperatu...mystified.html Switch gears for a moment and forget tank lighting, pretend you are an aspiring photographer and look at your tank like it is a model at a photoshoot. You just did some shots outside under natural lighting and the model looked great, then you go inside and to get some shots, and this time you want that same bright, natural look but toned towards blue. So you setup your cool white, low CRI lighting, add the blue suppliments and you bring in your model..... and she looks like a a ghoul. She is completely washed out, reds, oranges, greens, and yellows are gone, and there is simply no color definition, her color looks flat and lifeless.... So you break out the narrow band red and green supplimental lighting and adjust and adjust and adjust... But no matter what you do there is no real depth to her color, you just get bright peaks in the areas you added supplimental colors, without the fine gradients you get under natural sunlight, so whats wrong? So you seek out an experienced professional photographer and tell him your problem and ask him how to fix it, and he asks to see your lighting, so you break out the specs: •8x Cree XP-G Cool White LEDs run at 5w each (~70 CRI average) •8x Cree XP-E Blue LEDs run at 3w each (~470-480nm average) •10x Cree XP-E Royal Blue LEDs run at 3w each (450-460nm average) •4x Cree XP-E Green LEDs run at 3w each (◦520-535nm average) •4x Osram Oslon SSL Hyper Red LEDs run at 3w each (660nn) Now what do you think the first thing that experienced photographer will point out? Your base white lighting is completely wrong, why did you get the lowest CRI white lighting you can find? By definition it doesnt accurately represent colors.... Any professional wanting realistic colors is going to start with 90+ CRI white light, then tone it from there, not try to create high CRI light from scratch themselves at the shoot. This makes perfect sense right? No photographer would try to recreate the wheel. Why do we do that to ourselves when doing LED lighting for aquariums? For some silly reason someone started making LEDs for aquariums with low CRI cool white bulbs and it caught on (probably all that was available at the time). Then people wanted colors back that they used to have, because full spectrum lighting is available with both metal halides and T5, so they started adding color outside cool white and royal blue, striving to have all the colors show up accurately, then manufacturers (like ecotech) emulated this, and started selling fixtures that used this same idea, one that was flawed to begin with. So step away from that hodge-podge idea for a moment and consider what you would get if you started with high CRI warm whites, you might get something like this, where colors look natural and have both definition and gradients: That is actually a picture from SushiGirl of LED sump lighting. Now, what if you want some blue tone added to the white light? Here is a tank shot of a freshwater LED setup tank that I took, the clarity is not as good as SushiGirls but the color is accurate to my eye, it actually does have that nice purpleish glow in person too, thats not just an effect of the camera: So does anyone notice a difference in these 2 pictures from the standard flat washed out looking 1:1 Cool white LED setups?

07/22/2012, 09:39 AM	#2
tomservo Registered Member Join Date: Feb 2012 Location: Manitoba, Canada Posts: 332	This is why I based my reef lights around citizen multichip arrays.. Not only are they extremely good value, they are 85 CRI. I paid $16 each for the 64w 4000k versions I used. Surrounded them with a bunch (26-30) of 4w blues and some 420's. The results are amazing, I should take some pics of my friend's tank next time I visit. Pics of my tank are less than helpful, as I don't yet have any corals, just a maxi mini anemone. The lights I put over my friend's tank replaced eshine 60w units, with a marked improvement in color of corals and fish. The efficiency is right up there with any leading high CRI emitter, 75-85 lumens/watt. I just noticed looking up specs that they now have a 90 CRI 4000k emitter. product info: http://ce.citizen.co.jp/lighting_led...cts/index.html I used the CLL234A 5000k 85 CRI for my cichlid tank, and for my friend's fuge. CLL030-1212 4000k 85 CRI over the reefs. avnet has many of the emitters in stock (USA distributor) and the ones they don't, there's no minimum qty to special order! The real problem with the low CRI cool whites is the strong emphasis on the green/yellow spectra that our eyes are so sensitive to, which makes for crazy good lumen/watt ratings. You're not necessarily getting any more actual output power than the high CRI types, our eyes are just more sensitive to green/yellow. Last edited by tomservo; 07/22/2012 at 09:53 AM. Reason: supplied more/better info

07/22/2012, 02:04 PM	#7
sirreal63 Go Spurs Go!!! Join Date: Dec 2004 Location: Meadowlakes Texas Posts: 13,357	Sorry about that, bad drugs this morning, 30 ft is deep enough to give that overly blue look, and our tanks are really more closely related to a shallow reef environment with a more full spectrum of light. The wonderful thing about most of the corals in our tanks is they come from the full range of reef depths, we hopefully want to show our tanks in the best light so our lighting should be up to the task. This really hasn't been much of an issue with more traditional lighting but is with the more narrow lighting of most LEDs. I understand Joel's thread to mean just that, pay attention to the CRI of the lighting, it does make a difference. As far as depth, it varies greatly as well as the conditions of the reef. I don't think it is possible to say that one is healthier than the other. There are just too many variables,shallower reefs get more full spectrum, higher Par and more turbulent flow, etc etc. I prefer the Radium look but for growth it is hard to beat the 10k bulbs, it is just a preference and that is ok, it's what keeps everyone's tank from looking the same. :-) __________________ Jack No One has ever been seriously injured by using the search function. Alcohol, Tobacco and Firearms should be a convenience store, not a government agency. Current Tank Info: Reefing the Pentagon.

07/22/2012, 10:27 AM	#3
nyquist Registered Member Join Date: Jun 2012 Posts: 80	Just keep in mind that CRI is all about rendering colors as they appear in natural sunlight, defined by the spectral distribution of the sun at the earth's surface. High CRI lighting is good for accurately lighting extremely shallow ocean organisms (many algae, mangroves, shallow water sea grasses, etc). However, A reef sitting even just 10 meters below the surface of the ocean is not sitting in the typical spectral distribution from natural light, as water filters light passing through it. Red light has an attenuation coefficient nearly two orders of magnitude higher than blue or violet in water, thus accurately lighting a typical reef does not involve much red (or yellow or yellow-green). So a high CRI light source may look pretty and show you how the corals would look out of water, but it is often further from the natural lighting available to corals in the wild when compared to the blue and purple tinted lighting many LED fixtures provide.

07/22/2012, 02:31 PM	#8
nyquist Registered Member Join Date: Jun 2012 Posts: 80	true, reefs would be a little boring if everyone chose the same critters to display under the exact same lighting conditions

07/23/2012, 05:22 AM	#11
Pny Registered Member Join Date: Oct 2007 Location: Sweden Posts: 169	I'm afraid CRI is more or less useless for measuring LED output because of the way the CRI value is calculated... "The color rendering index (CRI) has been used to compare fluorescent and HID lamps for over 40 years, but the International Commission on Illumination (CIE) does not recommend its use with white light LEDs." Taken from: http://cool.conservation-us.org/byor...ring_index.pdf

07/23/2012, 12:15 PM	#14
joelespinoza Moved On Join Date: Dec 2011 Location: Galveston Posts: 417	The specific definition here is not important. The basic definition is simply that higher CRI rating means colors will be rendered more "accurately" to us. IE the color of the objects put under 100 CRI lights will look approximately the same to us as if they were lit by the sun, although the color of the light itself may or may not be the same color. This is something greatly lacking in cool white LED builds.

07/23/2012, 12:46 PM	#15
bhazard451 Registered Member. Join Date: Nov 2009 Posts: 1,900	No one has really nailed down a perfect ratio of CW:NW:WW yet. I used 6:3:3 to 24 royal blues + 4 violets + 2 cyan + 2 blue + 2 green + 2 red in a 48 led fixture, and I am pleased with the results. It resulted in a 12-14k look, which I enjoy compared to something more blue. I'm still tinkering with it, but some colors like orange really pop. I don't think anything on the market uses a ratio like this.

07/23/2012, 01:20 PM	#16
joelespinoza Moved On Join Date: Dec 2011 Location: Galveston Posts: 417	I am actually not sure why you would want to use any cool whites at all. Even my first neutral white setup is lackluster compared to the later Luxeon 2700k warm whites I have done.... I think the perfect white ratio is all high CRI whites. As far as supplimetal colors go, I dont think there is any point really. Violets are nice, but it takes a TON to make any noticable difference in a fixture. Reds, greens, blues and cyan just arnt required if you have whites that actually render colors accurately...

07/23/2012, 02:17 PM	#17
bhazard451 Registered Member. Join Date: Nov 2009 Posts: 1,900	Too many warm whites are extremely yellow, and would require that much more blue to balance it out. Running just the white channel even with 6CW mixed in on mine looks horrid, around 6-8k. I also disagree with needing a lot of violets. The difference is very noticeable with only 4 of them. Although they may look visually dim, there is an added fluorescence that actinic light provides compared to not having them. Same concept as adding 420nm actinic T5 supplementation.