# CRI is an archaic measurement that doesn't address real life rendition



## Electric_Light (Apr 6, 2010)

There are very limited applications where LEDs are suitable such as outdoor lighting where color quality is only a moderate importance, or where highly saturated colors are needed for decorative purposes.

However, these are some applications where I recommend against currently available LED lighting products: 

Textile industry
Apparel retail 
Printing industry
Polymer industry
Collision repair shops
Color matching 
Quality inspection 

Anywhere where the appearance of white matters are better served by high quality discharge lamp technology such as fluorescent and ceramic metal halide. 

CRI is a laboratory condition benchmark developed in the 1960s expressed as the average of deviation of the colors 1-8 in this chart. These color samples are dull looking colors and they do not exhibit any fluorescence. In the real world, what you see is a combination of reflected, transmitted and emitted fluorescence from the object. These color chips do not produce fluorescence. You could have a light source with a CRI score of 100, but fail to render color correctly in the real world. 










Light Emitting Decorations have spectral defect below about 450nm. While some materials like yellow and orange high lighters are activated by LEDs, fluorescence present in many glass, paper, polymer, coating and fabric products require spectrum not present in LEDs. 

This article talks about LEDs preventing detergent brightener from working, but this issue actually extends far beyond fabric brighteners. 

http://gizmodo.com/led-lights-are-ruining-laundry-detergents-white-brighte-1565070690

In the real world, many common objects such as coatings and plastics exhibit fluorescence and affect the way they look. 

I set my camera to "tungsten" white balance manually and shot at F3.3 1/250 at ISO 200. 

Top half was taken under a 40W incandescent. Bottom half under a CREE brand incandescent imitation 6W 2700K LED lamp which has a huge spike at deep blue and spectral defect in violet and deed red region that is expected from a 2700K black body emission. It's the same with commercially available LED products even those that boast CRI scores over 90. If the fluorescence induced appearance was unimportant, paper and textile industries would not spend money on brightening them. :laughing: LED disables this product feature. 

You can clearly see the difference between a minimally brightened white paper vs a brightened copy paper under the 40W incandescent lamp. The copy paper looks duller under the imitation incandescent and the contrast is visibly reduced. A white shirt and a cotton gauze look nearly the same under the LED, but the shirt and gauze are clearly contrasted under natural light, fluorescent light, incandescent light and best of all specialty high CRI metal halides providing a high CRI game number in excess of 90whiter outdoors, and commonly used gas discharge lighting technology. difference between the two is significantly weakened under a decorative light emitting source. 









In the collision repair industry where wide spectrum fluorescent lamps such as Chroma 50 (5000K rated at 90 CRI, and a wide band emission) are regularly used. Use of light source with a spectral defect such as LED can result in a finish that fine in the shop, but look like this in sun light. Current generation of ceramic metal halides are quite efficient and they have a spectrum very close to that of sunlight all the way into UVA and near IR.


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## chicken steve (Mar 22, 2011)

Light dude,
as usual you're well written and up on your forte' :thumbsup:, but could you please slow it up a tad for us garden variety luminaire jockeys:001_huh:?

This>>>?



> These color samples are dull looking colors and they do not exhibit any fluorescence. In the real world, what you see is a combination of reflected, transmitted and emitted fluorescence from the object.


~C:001_huh:S~


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## daveEM (Nov 18, 2012)

Might need some communication courses in order to talk to some of us electricians. 

From here...
http://en.wikipedia.org/wiki/Readability



> In 1947, Donald Murphy of Wallace's Farmer used a split-run edition to study the effects of making text easier to read. They found that reducing from the 9th to the 6th-grade level increased readership 43% for an article on 'nylon'. There was a gain of 42,000 readers in a circulation of 275,000. He found a 60% increase in readership for an article on 'corn'. He also found a better response from people under 35
> 
> The two publications with the largest circulations, TV Guide (13 million) and Readers Digest (12 million), are written at the 9th-grade level.[5] The most popular novels are written at the 7th-grade level. This supports the fact that the average adult reads at the 9th-grade level. It also shows that, for recreation, people read texts that are two grades below their actual reading level


Also have a look here...
http://www.impact-information.com/impactinfo/literacy.htm


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## Big John (May 23, 2010)

I ain't a lighting guy but what I gathered is that LEDs cannot reproduce the appearances created in by natural light despite technical specifications that are implying they do. So _Electric Light_ is arguing that they standards for rating lights need to be modified.

The interesting part to me is the photo of the two-tone truck. Assuming that is really a deficiency caused by LED lighting that could not have been prevented by carefully examining the LED specifications, then there would appear to be a serious problem in how we are rating fixtures.

But: I don't understand the claim that LEDs do not encourage fluorescence. I've seen articles lately that indicate people are concerned about LEDs precisely because they can may be putting out too much near-ultraviolet and ultraviolet light, which is the component of the spectrum that _causes _materials to fluoresce. How do you reconcile those two claims?


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## chicken steve (Mar 22, 2011)

> daveEM said:
> 
> 
> > Might need some communication courses in order to talk to some of us electricians.
> ...


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## chicken steve (Mar 22, 2011)

Big John said:


> How do you reconcile those two claims?


Especially if the paint shop guy is on the horn screaming.....:no:~CS~


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## Expediter (Mar 12, 2014)

chicken steve said:


> Light dude,
> as usual you're well written and up on your forte' :thumbsup:, but could you please slow it up a tad for us garden variety luminaire jockeys:001_huh:?
> 
> This>>>?
> ...


 Steve, I am very surprised that you are the one who posted this. From your posts, you seem to be extremely well read. Much to the consternation of others. 

BTW, I love threads like this. I learn a lot. Thanks lightguy:thumbsup:


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## Big John (May 23, 2010)

However, having said the above, looking at OP's post history it seems like he has a pretty serious ax to grind against LED lighting. It appears that most of his posts where that is the topic are just complaints about how it sucks, so that makes me take this thread with a much bigger grain of salt.

Without a doubt, there are problems with LEDs, but from where I stand they are the clear winner for the future of lighting technology.


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## Meadow (Jan 14, 2011)

Big John said:


> However, having said the above, looking at OP's post history it seems like he has a pretty serious ax to grind against LED lighting. It appears that most of his posts where that is the topic are just complaints about how it sucks, so that makes me take this thread with a much bigger grain of salt.
> 
> Without a doubt, there are problems with LEDs, but from where I stand they are the clear winner for the future of lighting technology.


I have a serious ax to grind with AFCIs :laughing::jester:, but as with every technology it has its place. I do not believe LEDs will replace everything, but I can think tons of applications where they win hands down. Certainly efficiency where light is not a great concern like road ways. And when compared to low pressure sodium LED roadway lighting looks like daylight quality lighting.


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## chicken steve (Mar 22, 2011)

Expediter said:


> Steve, I am very surprised that you are the one who posted this. From your posts, you seem to be extremely well read. Much to the consternation of others.
> 
> BTW, I love threads like this. I learn a lot. Thanks lightguy:thumbsup:


I'm just being _honest_ Expediter. 

Way back in my fowl past, i was an engineering tech for a computer based optical R&D lab. The spectroscopic science involved drew sorts with more alphabet after their names, than their names themselves.

Such sorts were educational for anyone north of a stump to be around , but i'd caution anyone with the naivety to ask about the qualities of _'fluorescence'_ to pack a lunch, and that'd be for the _short _answer....

~CS~


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## Southeast Power (Jan 18, 2009)

Expediter said:


> Steve, I am very surprised that you are the one who posted this. From your posts, you seem to be extremely well read. Much to the consternation of others.
> 
> BTW, I love threads like this. I learn a lot. Thanks lightguy:thumbsup:


Steves posts are much different than a year or so ago.
Maybe he's passing along his secret formula to the OP.


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## Electric_Light (Apr 6, 2010)

The section is called "lighting design", meaning that its not just for the guys that hang light fixtures. This field is inclusive of lighting designers, specifiers, applications engineers, energy code specialists and buyers who influence decision to buy/not buy LEDs, offer/not offer rebates, developing codes and purchasing guidelines. 

Unfortunately, the absence of information and abundance of misinformation is causing LEDs to get precariously specified. "CRI tells everything there is about how color is rendered" is a common misconception. In fact, CRI number does not address white or clear objects at all even though the light source significantly affect their rendition. Until industry standards are developed that address real world color renditions, the knowledge of spectral defect in LEDs is useful in knowing what things to look for in pre-commitment evaluations. 



chicken steve said:


> Light dude,
> as usual you're well written and up on your forte' :thumbsup:, but could you please slow it up a tad for us garden variety luminaire jockeys:001_huh:?
> This>>>?












The bluish glow is called "fluorescence" and it didn't actually come from the light source. In the above example, tonic water absorbs the UV and produces its own bluish glow. Look at several white objects under black light and you'll see that some look dull like the lid in that picture while some light up like the tonic water. You could actually see the difference between tonic water and clear soda under natural light if you pay attention. 

What we see is a combination of light that passes through, reflects as well as emitted by the object. They all contribute what we actually see. I am saying that missing emissions below 450nm in light sources with spectral flaws such as LED lighting products suppress proper color rendition. You'll lose the "brighter than white" appearance. They just look duller. LEDs can also hide defects visible under ordinary light. 



Big John said:


> But: I don't understand the claim that LEDs do not encourage fluorescence. I've seen articles lately that indicate people are concerned about LEDs precisely because they can may be putting out too much *near-ultraviolet and ultraviolet light*, which is the component of the spectrum that _causes _materials to fluoresce. How do you reconcile those two claims?


The concern you bring up involves deep blue LED is under investigation for possible long term accelerated degradation of retina which are the image forming pixels in our eyes. While ultraviolet is damaging too, it's stopped at the cornea. The articles were wrong or you misinterpreted them. LEDs have disproportionately high amounts of potentially retina damaging 450nm *shortwave length blue*. It's the same blue used by dentists to set dental cements. They use a colored safety goggles when they use the light. Many items actually glow under blue. Fluorescent yellow and fluorescent orange being some examples. However, most fabric and paper products, and some plastics are only responsive to shorter wavelength not present in LED lighting. This range of spectrum is present in incandescent, fluorescent, HIDs, etc. 

Some plastic parts and coatings exhibit different fluorescence. Two components that appear to have a decent color match under lol LED light can actually have a terrible color mismatch under normal lighting. Most paint color match stations do not involve comparison of paint samples with significant fluorescence. This changes when you're comparing plastic parts and clear coating and there comes the issue like the two-tone truck which shows different appearance depending on lighting. 

Lay high grade retail poster or a copy paper next to a non-brightened white paper like paper towel. Compare them alongside under a 2700K lamp, then compare them under a 60W incandescent lamp. White fabrics and bright papers look duller under LED lighting. They'll all look like yellowed paper. 

The spectral flaw in sub 450nm is a spectral flaw that's distinctively LED lighting. MH, fluorescent, etc don't have a perfect spectrum, but they do not have this specific flaw. 

Another highly important design consideration is that LED products specs generally allow permanent degradation of 30% during lifetime which is worse than every light source except metal halide. There is a leeway for outdoor use as LEDs are not as bad as traditional metal halide in lumen depreciation, but current energy codes fail to address the life time rating standards used by the LED industry that allow them to have sub-mediocre levels of lumen depreciation. If the fixture does not have an active power level control, the initial foot candle level needs to exceed the design level by 42%. Active compensation is just a fancier way of saying LED decay compensator that increase the input power as the fixture ages to maintain the same output level.

So, when energy performance calculations are done, the wasted energy needed to over illuminate by 42% or the added energy the fixtures use to maintain the same initial level needs to be factored in. Active LED degradation compensation adds significantly to material cost. 

Color shift limits, output maintenance and maintained efficacy more stringent than 70% are well worth adding into sustainability standards specifications instead of specifying LED based products on just the "out of the box" specs. 

http://www.designingwithleds.com/smithsonian-led-retrofit-sees-power-savings-color-shift/


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## macmikeman (Jan 23, 2007)

chicken steve said:


> Light dude,
> as usual you're well written and up on your forte' :thumbsup:, but could you please slow it up a tad for us garden variety luminaire jockeys:001_huh:?
> 
> This>>>?
> ...


Wow, Chicken Steve is telling somebody to make the gibberish easier to comprehend................. truly amazing post there Steven....:laughing:


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## Meadow (Jan 14, 2011)

While I know little of lighting; this is exactly why I love forums like this. Information that no one will ever tell me can be found here, a long with a serous intent to advance our trade :thumbup::thumbup:

Electric_Light: Thanks you for your knowledge!


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## V-Dough (Jul 22, 2014)

Thanks for your article, Electric Light. I never realized UV light and fluorescence play such an important part in visible spectrum. Hopefully some manufactures soon realize that its all about replicating natural spectrum and not lumens per watt...


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## JBrzoz00 (Nov 17, 2013)

I've been wondering how LEDs would work with artwork. From this I take it that a halogen MR16 is still the best way?


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## Electric_Light (Apr 6, 2010)

I don't have a definitive answer. It's trial and error. Perhaps one or two in a cardboard booth painted the same as intended rooms as a mock-up. 

CRI and such are measured values based on test protocols. It does not address pleasant/unpleasant at all. It's really hard to beat the expected results and consistency of halogen. From the pile in a clearance bin to high-end lamp, they produce the same quality light. Their only limitations is making light that's whiter than 3000K. 

LEDs have a huge variation from brand-to-brand, batch-to-batch in consistency. You had better bought 5-10% spare lamps or if one or two fails, they may not be able to avoid an obviously noticeable difference.


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## Almost always lurkin (Jul 30, 2014)

How valuable is the artwork? Something to consider is that UV light causes damage over time.


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## Electric_Light (Apr 6, 2010)

Almost always lurkin said:


> How valuable is the artwork? Something to consider is that UV light causes damage over time.


The boundary between ULTRAviolet and violet is arbitrary based on human vision. It's not based on a physical phenomena like the freezing point of water. Visible light contributes significantly to fading at sufficient intensity. 

You may want to read this:
http://cool.conservation-us.org/byform/mailing-lists/cdl/2010/0361.html


From that website:
"Since it is well established that light-sensitive
materials--typically illustrated by Japanese wood block prints, dyed
textiles, watercolors, pastels, color photographic images,
biological specimens etc.--are damaged (ie undergo color shift such
as loss of coloration--fading, darkening, yellowing or color-shift)
by radiant energy *within* the human visible spectrum, *any
light-sensitive material whose damage spectra (within the absorption
spectra as opposed to the reflection spectra) contains any of these
isolated LED output peaks would undergo damage at 20% to 400% faster
rates than if lit at the same light levels with an unfiltered MR 16." *

Lighting LED products are of the solid state fluorescent lamp type which uses royal blue 450 nm LED encapsulated in a phosphor blend which glows yellow when struck with blue light. The pass-though blue and yellow from fluorescence forms white light. 

The energy content of white light from LED is extremely high in the deep blue light in 440-460nm range.. LEDs also have a distinctive spectral flaw between blue and green which includes turquoise, aqua, cyan etc.


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## LARMGUY (Aug 22, 2010)

Electric_Light said:


> There are very limited applications where LEDs are suitable such as outdoor lighting where color quality is only a moderate importance, or where highly saturated colors are needed for decorative purposes.
> 
> However, these are some applications where I recommend against currently available LED lighting products:
> 
> ...


Finally something I can understand!

Lightdude,
I'm trying to set up a small studio area for my artwork. I have a small 10 X 12 bedroom with offwhite walls. I only need about 1/4 to 1/2 of it to be illuminated for working. I thought of LED's but my dislike for their harshness and color changing capabilities and your post has changed this.

I have tried an Ott Light which is supposed to be full spectrum but I feel I get no full range of color. When I mix lamps I get spotty color.


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## LARMGUY (Aug 22, 2010)

What can I use to bring out the whites and the full color spectrum of my artwork?

Is there a specific number on a fluorescent I need to be looking for?


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## mescalero1 (Jan 15, 2015)

*First off, CRI is not "archaic" like someone would like you to believe. It is a reference and that is all. It has actually been amended with more tones, which the OP neglected to mention or does not know. I am sure that has something to do with his anti-LED rhetoric. There is also another scale that need to be researched more before it can become a standard and that is the Color Quality Scale. If you research LED technology, you will find out that newer LED technology eliminates the blue LED and is using amber in a RGBA configuration instead of RGBW. You can read about that here:

http://www.nrel.gov/technologytransfer/technologies_led.html

Anyone in lighting should really not listen to rhetoric and go to websites like 
http:www.led-professional.com/ 
and view the latest LED technologies. The examples the OP is giving are dated and "archaic". It is amazing how some people keep trying to rub sticks to make fire.*


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## Electric_Light (Apr 6, 2010)

LARMGUY said:


> Finally something I can understand!
> 
> Lightdude,
> I'm trying to set up a small studio area for my artwork. I have a small 10 X 12 bedroom with offwhite walls. I only need about 1/4 to 1/2 of it to be illuminated for working. I thought of LED's but my dislike for their harshness and color changing capabilities and your post has changed this.
> ...


What color temperature do you want? Both natural daylight and incandescent lamps are full spectrum with 100 CRI, with respect to the same kelvin temp, but the colors will render differently with different color temperature just like incandescent lamp and sun light renders differently. 

Lamps like GE Reveal makes some colors look more vibrant by inducing a distortion. A distortion isn't what you want if you want accurate rendition. Same with display case lamps like Promolux meant to provide favorable distortion to make meat look redder. 



LARMGUY said:


> What can I use to bring out the whites and the full color spectrum of my artwork?
> Is there a specific number on a fluorescent I need to be looking for?


Make sure to use electronic ballasts or you'll have an intolerable flicker. You're not setting up a bunch of fixtures, so shop the lamps first. Even T12 electronic ballasts are readily available. 

There are some temperatures like 5500K from minor brands, but the selection and availability depends on the supply house, so its better to stick with the more commonly available 5000K which are reasonably close to D50 standard adopted by the graphic arts industry. The output isn't too high. For the same wattage, they're about 2/3 the lumens of ordinary RE80 lamps. Spectral performance is excellent, rendition is great and they're not expensive. $5-10/lamp range. 

*5000K *
I would go for the 5000K 90 CRI T12 as they have good availability through many channels. This is the common choice for graphic arts, dental labs, auto body etc. It's a wide spectrum type with far less spectral flaws than LEDs most particularly in 400-450nm and there's no huge valley between blue and green which is important in proper rendition of cyan. These lamps would would be called /950 or C50 in the professional market, but they're called various different things in the consumer market. Look for lamps that has specs 5000K and a CRI rating of 90-92. They're commonly available under various different names at consumer stores. If you can't find them at the supply house, hit up Home Depot, Lowe's or hardware stores. These lamps can feel harsh and uninviting, but you'd be amazed how well colors of artwork, paint and fabrics are rendered. Nearly as good as sunlight through windows. 

T8: 
Sylvania FO32T8/950 (generally used for sign lighting) 
General Electric 66343 F32T8/C50/ECO

The problem is that some lamps sold as "full spectrum" are actually just 850 or 865 lamps, especially CFLs. 850s have problem with cyan/blue green colors, but bring out shades of whites far better than light emitting decorations. 

*4100K *
F40T12 CWX Cool white deluxe. 
F40T12 or F34T12 941
F40T12 Cool White Supreme 
Find CRI 88 or higher. If it's not, it's just an 841 lamp. 

T8 
F32T8/UT General Electric consumer lamp 66836 Try Ace Hardware. 
http://genet.gelighting.com/LightProducts/Dispatcher?REQUEST=COMMERCIALSPECPAGE&PRODUCTCODE=66836

You could also consider exceptional color rendition using indirect lighting using Sherwin-Williams SW-7071 paint on walls and PAR ceramic metal halide which has a very good continuous spectrum from UVA to near IR with very low spectral defect unlike light emitting decorations. This provides the best shadow reduction. 

http://www.usa.lighting.philips.com/connect/tools_literature/downloads/p-5432.pdf

http://www.usa.lighting.philips.com/pwc_li/us_en/connect/tools_literature/downloads/151423.pdf

*3000K:*
Tungsten halogen is the best. Those 72-75W eco halogen meant to replace 100W lamps work excellent. 

Philips F32T8/TL930, but you'll likely have to special order a whole case or more.


If you're proofing posters intended to be used in spaces lit by light emitting solid state decorative lights, use those lights so you can see how they look in the intended environment.


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## LARMGUY (Aug 22, 2010)

Electric_Light said:


> What color temperature do you want? Both natural daylight and incandescent lamps are full spectrum with 100 CRI, with respect to the same kelvin temp, but the colors will render differently with different color temperature just like incandescent lamp and sun light renders differently.
> 
> Lamps like GE Reveal makes some colors look more vibrant by inducing a distortion. A distortion isn't what you want if you want accurate rendition. Same with display case lamps like Promolux meant to provide favorable distortion to make meat look redder.
> 
> ...


Great answer! Thanks! I would much rather have indirect lighting and I think that's the way to go. What kind of indirect fixtures would accommodate those Philips lamps?


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## chicken steve (Mar 22, 2011)

> mescalero1 said:
> 
> 
> > *First off, CRI is not "archaic" like someone would like you to believe. It is a reference and that is all. It has actually been amended with more tones, which the OP neglected to mention or does not know. I am sure that has something to do with his anti-LED rhetoric. There is also another scale that need to be researched more before it can become a standard and that is the Color Quality Scale. If you research LED technology, you will find out that newer LED technology eliminates the blue LED and is using amber in a RGBA configuration instead of RGBW. You can read about that here:
> ...


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## Electric_Light (Apr 6, 2010)

mescalero1 said:


> First off, CRI is not "archaic" like someone would like you to believe. It is a reference and that is all. It has actually been amended with more tones, which the OP neglected to mention or does not know.


It's outdated. Limitations of CRI have been known for a long time and simply stating just the CRI is completely unacceptable in communicating the color reproduction qualities. We just don't have a new system that everyone can agree upon. Current stuff makes no sense to people other than some highly technical stuff that makes no sense to people other than specifiers and lighting designers. 

ANSI and ISO have requirements that is used in the printing industry. 5000K 90-92 CRI fluorescent lamps are quite cheap and meet these standards. 

There's a measurement called full spectrum index, but its defined based on equal energy on lower and higher extreme of visible spectrum which is at about 5500K. 

http://www.lrc.rpi.edu/programs/nlpip/lightinganswers/fullspectrum/comparisons.asp

Not many products can satisfy the cut off requirements. The few that can are the 5000K >90 CRI lamps I mentioned which are inefficient (50-60 LPW) but cheap. Short arc xenon (inefficient, extremely expensive) and high color rendition ceramic metal halide like the Philips one I linked earlier fares well too. There are some LED based products for graphic arts, but they're not based on the same design as LED lighting products. Calibration stability over time, across temperature range, consistent chromaticity between multiple fixtures, and spectral stability when dimmed are all questionable. They're also *EXTREMELY* EXPENSIVE meaning and that they cost by an order of magnitude or so more compared to a comparable C50 fluorescent system. I am sure LED based color critical systems are costly to operate as well since you'll likely need to send it in to the calibration lab annually(or more often) or after every so many hours of use to guarantee they operate within specs of C50 lamps. Color matching fluorescent lamps don't last that long. You don't use them until they burn out. You have to burn-in the lamps-in initially for 100 hours or so, then they're re-lamped after a few thousand hours. Lamps only cost about 5 bucks a piece, so it's not too expensive to re-lamp every 5,000 hours. LED based unit works by coordinating multiple different color LEDs. Since they're far beyond expensive to relamp often, the coordination between each colored LEDs need to be realigned at the calibration lab at a cost of several hundred dollars per service. Chromaticity shift is a common cause of LED product failure. It's just ugliness for street lights, but if an LED color match light source can not be made to hold calibration through a regular interval or the calibration adjustment do not make it come in within limits, then that equipment is trash. If you're gonna use LED color proof lights, I hope the lease payment includes semi-annual on-site professional calibration. 

The common CRI just uses average of colors 1-8. If 7 out of 8 are 95 but one is 70, the CRI is 91.9. This creates a problem akin to wearing four different sized tires even though the average of four looks very good. ANSI and ISO used by the graphic arts industry LIMIT the maximum each of the R values is allowed to deviate to limit lopsided distortion. 

The additional colors 9-14 are NOT included in calculation of CRI and they still do not problems caused by spectral defect. 



mescalero1 said:


> I am sure that has something to do with his anti-LED rhetoric. There is also another scale that need to be researched more before it can become a standard and that is the Color Quality Scale. If you research LED technology, you will find out that newer LED technology eliminates the *blue LED* and is using amber in a RG*B*A configuration instead of RG*B*W. You can read about that here:


Perhaps you work for the LED industry, but in the internet marketing department and have experience in social media and advertisement, but apparently none in this technology. You already told us in your very first post here that you have absolutely NO IDEA how LED lighting products work. :laughing: :laughing: :laughing: irate: 

I don't appreciate having my posts called out as "anti LED rhetoric" by someone who do not understand lighting technology whatsoever. 



mescalero1 said:


> Anyone in lighting should really not listen to rhetoric and go to websites like (some site you're probably affiliated with) and view the latest LED technologies. The examples the OP is giving are dated and "archaic". It is amazing how some people keep trying to rub sticks to make fire.[/B]


Well, says the marketing guy who just created an account and already proved in his first post that he has zero understand of the technology he was sent to represent?

Here's a .edu: 
In both abbreviations you dropped, the letter B stands for blue. 

White LED lighting is not possible without blue LEDs within the realm of current commercially realistic technology. >99% of commercially deployed LED lighting products is the blusolid state fluorescent lamp known under the industry jargon pcLED. RGB, which stands for red, green, blue means the product uses three colors of LEDs to create white light. It's not in common use for lighting applications. 

Theory of operation for solid state fluorescent lamps and a conventional fluorescent lamp. 











These are two mainstream products commonly called "LED light bulbs" that is based on the solid state fluorescent lamp technology. They use blue LEDs through a yellow emitting fluorescent phosphor. The yellow light from phosphor combined with blue passing through makes the light look white. 

The clear "light bulb" is the equivalent of blue LED used in SSFL and a representation of what a conventional fluorescent looks like without the phosphor coating. Conventional fluorescent lamps use a deep ultraviolet emission and they're made from glass that do not pass this range of UV. Light that comes out is made of visible light that exists along with UVC and phosphor generated light. 










Here's a demonstration of commercially sold solid state fluorescent lamp dismantled and excited by an external blue LED. This SSFL uses the phosphor chemical applied directly on the chip as opposed to the design shown in the first picture. It is the cheapest available technology. 










The phosphor on fluorescent lamps work by absorbing a shorter wavelength light, then re-radiating at a longer wavelength. There's a gap between the two. In conventional FL lamps, the gap falls within the range of UV that you don't want coming out anyways, so it's a non-issue. 

However, SSFLs use a blue LED, so a serious spectral flaw occurs right in the middle that affects the quality of light. As you can see, this is the typical spectral flaw you'll see in SSFL LED products. 

Here's what the spectrum of the common white LED looks like. I put X's at the characteristic LED spectral defects. 









Note that there are two dominant flaws. 450nm and below. This covers violet and UVA. It affects direct rendition as well as objects having fluorescence.

Gaping valley in between blue and green. It slaughters gamut range or making them less able to reproduce color accurately. To avoid this gap, it requires the use of ultraviolet excitation which is not currently economically feasible. Another method is to use discrete colored LEDs to plug up the two valleys, but the coordination requires intricate calibration process to guarantee stability over time and to ensure they age equally among multiple lumuniares. 
You could use a whole bunch of LEDs to cover all the way from deep red to long wave ultraviolet, but each one of the LEDs will shift in performance differently and unless the degradation is perfectly predicted and programmed in before shipping. UV-Violet-Cyan-Blue-Green-Orange-Yellow-Red octochromatic systems can be built, but it makes already highly expensive LED lighting unaffordably expensive. They'll suffer degradation outside of prediction in reality, so don't forget the highly expensive calibration service they're going to require regularly. 
If any luminaire or LED modules require replacement for any reason, the repair is similar to an auto body repair. It requires intricate color matching process to ensure uniformity in appearance now, as well as uniformity in aging of existing luminaires and new LEDs in the repaired luminaire. A very expensive service that will probably require multiple service calls.


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## Texas_LED_Guru (Mar 1, 2013)

Electric_Light said:


> In the collision repair industry where wide spectrum fluorescent lamps such as Chroma 50 (5000K rated at 90 CRI, and a wide band emission) are regularly used. Use of light source with a spectral defect such as LED can result in a finish that fine in the shop, but look like this in sun light. Current generation of ceramic metal halides are quite efficient and they have a spectrum very close to that of sunlight all the way into UVA and near IR.


Many different probable causes there & you blame it on LED's.

Looks like nothing more than a poorly mixed gallon of paint to me.

Worker could have came to work with a hang over, etc. etc. Many different possibilities at play here.


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## MHElectric (Oct 14, 2011)

:laughing:

The only thing I really hate as much as he hates LED's, is meatloaf. Maybe I'll start a thread each week about the danger & horrors of meatloaf, might stir up some interesting discussions.


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## papaotis (Jun 8, 2013)

Texas_LED_Guru said:


> Many different probable causes there & you blame it on LED's.
> 
> Looks like nothing more than a poorly mixed gallon of paint to me.
> 
> Worker could have came to work with a hang over, etc. etc. Many different possibilities at play here.


if that color match is from a hangover he should be fired!


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## Electric_Light (Apr 6, 2010)

Texas_LED_Guru said:


> Many different probable causes there & you blame it on LED's.
> 
> Looks like nothing more than a poorly mixed gallon of paint to me.
> 
> Worker could have came to work with a hang over, etc. etc. Many different possibilities at play here.


CRI ignores fluorescence and assumes that it doesn't contribute much. In reality, it does. 

The point I am addressing with the picture of the truck is a phenomena called metamerism where the object appears the same under one lighting, but different under another. It's a problem when products consisting of two different materials appear the same under quality inspection but drastically different outdoors. 

Lighting devices of the solid state fluorescent lamp that use blue LEDs to trigger a wide band yellow phosphor are completely deficient in light energy in violet and ultraviolet region, and there's a distinctive flaw in blue and green affecting rendition of metallic green, turquoise and aqua most notably in pigment colored objects. The overwhelming majority of "LED lighting" is of the blue LED + yellow phosphor solid state fluorescent lamp variety.


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