How can something be near perfect CRI with a big blue spike?

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autumncrown
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How can something be near perfect CRI with a big blue spike?

e.g. the SW45k: https://i.imgur.com/CfehtBR.png
Or SST 20 4000k: https://i.imgur.com/ldEQbh7.png

There is a big spike at 450 nm. I know WHY this is – because they start with a blue LED. But is that why the r12 value is low? How can such a large deviation only result in a couple CRI points lost?

Related question: How much does it matter that virtually no white LEDs have proper extension into the 700 nm+ range?

Edited by: autumncrown on 07/28/2021 - 11:28
thefreeman
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R12 is not counted in th Ra value, only R1 to R8.

Rf (TM-30) which is an average of the 99 color samples at the bottom of the report is lower (90) because it takes several blue samples into account.

autumncrown
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Interesting. Anyone have any idea how much this blue spike subjectively affects light quality?

thefreeman
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Not much I’d say, what the data shows is that blues are more saturated and tend towards purple (color vector graphic), in reality I think this is difficult to see.

Edit :

Quote:
Related question: How much does it matter that virtually no white LEDs have proper extension into the 700 nm+ range?

I don’t think we can see 700nm

nottawhackjob
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To help verify the CRI of your particular flash, all ya have to do is get the Ozark Trail OT 50L at yer local Walmart for $1.00 as stated in my signature.

This will tell you if the TCR matches the CRI that you thought should be there.

Nothing can better define your particular unique flash’s CRI expectations than reality. Grad

“In many things in order to truly understand the small picture you have to understand the big picture first.”

True Color Rendition (TCR)/Simplified Definition: “On a scale of 1 to 10, with 10 being the highest rating, a TCR will equate to what true colors you see in sunlight vs the same object’s colors you see when illuminated with a flashlight. The closer the two are, the higher the TCR rating will be.”

The TCR Reference Standard is the Walmart Ozark Trail OT 50L , Model No. 6103.
It has a TCR rating of ‘10’. $1.00 including batteries.

autumncrown
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Did you make TCR up based on a particular emitter you like? Wouldn’t NCR be more accurate? (nottawhackjob color rendering)

Inexorabill
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Quote:
I don’t think we can see 700nm

730nm far red lights exist and you can see them ok but they are a lot dimmer than shorter wave red lights.

Illuminant E master race.

nottawhackjob
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autumncrown wrote:
Did you make TCR up based on a particular emitter you like? Wouldn’t NCR be more accurate? (nottawhackjob color rendering)

TCR is a subjective rating to a particular flash. Every flash is different. Hence every emitter is different. Granted, web-consensus can then become a strong or even better indicator of production consistency. This is where TCR fills a gap that CRI can’t provide.

If you think your eyes are inferior to CRI then ya shouldn’t care. Just buy watt the CRI sez and if you’re unhappy with watt ya got then ya can blame CRI, right? Grad

“In many things in order to truly understand the small picture you have to understand the big picture first.”

True Color Rendition (TCR)/Simplified Definition: “On a scale of 1 to 10, with 10 being the highest rating, a TCR will equate to what true colors you see in sunlight vs the same object’s colors you see when illuminated with a flashlight. The closer the two are, the higher the TCR rating will be.”

The TCR Reference Standard is the Walmart Ozark Trail OT 50L , Model No. 6103.
It has a TCR rating of ‘10’. $1.00 including batteries.

autumncrown
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Seems like CRI can help people make educated guesses about what they might like and tm 30 is even better.

nottawhackjob
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autumncrown wrote:
Seems like CRI can help people make educated guesses about what they might like and tm 30 is even better.

I never said it didn’t. Grad

Butt in the end of it an educated guess is still a guess, right?

“In many things in order to truly understand the small picture you have to understand the big picture first.”

True Color Rendition (TCR)/Simplified Definition: “On a scale of 1 to 10, with 10 being the highest rating, a TCR will equate to what true colors you see in sunlight vs the same object’s colors you see when illuminated with a flashlight. The closer the two are, the higher the TCR rating will be.”

The TCR Reference Standard is the Walmart Ozark Trail OT 50L , Model No. 6103.
It has a TCR rating of ‘10’. $1.00 including batteries.

thefreeman
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Inexorabill wrote:
Quote:
I don’t think we can see 700nm
730nm far red lights exist and you can see them ok but they are a lot dimmer than shorter wave red lights.

Looking a a few 730nm LED Datasheets a part of their spectrum are in the Visible range which would be what we would see, just like an UV LED also emits in the visible range.

kennybobby
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Quote:
There is a big spike at 450 nm. I know WHY this is – because they start with a blue LED. But is that why the r12 value is low? How can such a large deviation only result in a couple CRI points lost?

What do beam shots look like—does a blue tint dominate the beams of these two?

Now i used to think that i was cool,
drivin' around on fossil fuel,
until i saw what i was doin',
was drivin' down the road to ruin. --JT

autumncrown
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Depends on the lighting and tint bin. The sw45k seems fairly tightly binned and most people would say the SW45k is pink, but it is blue compared to warmer lights or at night. I have had 3 bins of the SST-20 4000k and they range from yellow-green to white-blue-pink in tint.

Unheard
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thefreeman wrote:

Looking a a few 730nm LED Datasheets a part of their spectrum are in the Visible range which would be what we would see, just like an UV LED also emits in the visible range.


Interesting. Our Bundesamt für Strahlenschutz BfS gives a range of visible light up to 780nm. Is this a mean/max thing? Or don’t I understand the photopic luminosity function (likely Big Smile )?

Smile, you cannot kill them all.

nottawhackjob
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Question for all.

Are you willing to trade tint or color temperature for TCR?

“In many things in order to truly understand the small picture you have to understand the big picture first.”

True Color Rendition (TCR)/Simplified Definition: “On a scale of 1 to 10, with 10 being the highest rating, a TCR will equate to what true colors you see in sunlight vs the same object’s colors you see when illuminated with a flashlight. The closer the two are, the higher the TCR rating will be.”

The TCR Reference Standard is the Walmart Ozark Trail OT 50L , Model No. 6103.
It has a TCR rating of ‘10’. $1.00 including batteries.

raccoon city
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nottawhackjob wrote:

Question for all.

Are you willing to trade tint or color temperature for TCR?

I'm sure some people are willing to make a trade off for CRI, but "TCR" isn't a real thing.  :P

autumncrown
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I’m not convinced “TCR” raises the quality of discussion. It seems more like a distraction from the subject of the thread.

Unheard
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Whacky, your signature grows at a frightening speed. Is there really no limit, or have you found a way around it?

Smile, you cannot kill them all.

raccoon city
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Unheard wrote:

Whacky, your signature grows at a frightening speed. Is there really no limit, or have you found a way around it?

There is no limit on how big a signature can be, but if it gets too big people might complain.  :BEER:

nottawhackjob
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Unheard wrote:
Whacky, your signature grows at a frightening speed. Is there really no limit, or have you found a way around it?

I think it has found a limit. For now. LOL

“In many things in order to truly understand the small picture you have to understand the big picture first.”

True Color Rendition (TCR)/Simplified Definition: “On a scale of 1 to 10, with 10 being the highest rating, a TCR will equate to what true colors you see in sunlight vs the same object’s colors you see when illuminated with a flashlight. The closer the two are, the higher the TCR rating will be.”

The TCR Reference Standard is the Walmart Ozark Trail OT 50L , Model No. 6103.
It has a TCR rating of ‘10’. $1.00 including batteries.

nottawhackjob
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raccoon city wrote:

Unheard wrote:

Whacky, your signature grows at a frightening speed. Is there really no limit, or have you found a way around it?


There is no limit on how big a signature can be, but if it gets too big people might complain.  alt=:" />

I’ll reduce it when more and more understand and accept the reasoning behind TCR.

“In many things in order to truly understand the small picture you have to understand the big picture first.”

True Color Rendition (TCR)/Simplified Definition: “On a scale of 1 to 10, with 10 being the highest rating, a TCR will equate to what true colors you see in sunlight vs the same object’s colors you see when illuminated with a flashlight. The closer the two are, the higher the TCR rating will be.”

The TCR Reference Standard is the Walmart Ozark Trail OT 50L , Model No. 6103.
It has a TCR rating of ‘10’. $1.00 including batteries.

nottawhackjob
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autumncrown wrote:
I’m not convinced “TCR” raises the quality of discussion. It seems more like a distraction from the subject of the thread.

Yeah you have a point. Didn’t mean to distract at an expense. I’ll start my own thread on this subject. Maybe.

“In many things in order to truly understand the small picture you have to understand the big picture first.”

True Color Rendition (TCR)/Simplified Definition: “On a scale of 1 to 10, with 10 being the highest rating, a TCR will equate to what true colors you see in sunlight vs the same object’s colors you see when illuminated with a flashlight. The closer the two are, the higher the TCR rating will be.”

The TCR Reference Standard is the Walmart Ozark Trail OT 50L , Model No. 6103.
It has a TCR rating of ‘10’. $1.00 including batteries.

raccoon city
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nottawhackjob wrote:

I'll reduce it when more and more accept and understand the reasoning behind TCR.

Don't hold your breath.

TCR will never take off because it is subjective, and not scientifically measurable.

nottawhackjob
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raccoon city wrote:

nottawhackjob wrote:

I’ll reduce it when more and more accept and understand the reasoning behind TCR.


Don’t hold your breath.


TCR will never take off because it is subjective, and not scientifically measurable.

I think you’ll be proven wrong.

PS. It’s Autumn’s thread. I’ll respectfully bow out of it.

“In many things in order to truly understand the small picture you have to understand the big picture first.”

True Color Rendition (TCR)/Simplified Definition: “On a scale of 1 to 10, with 10 being the highest rating, a TCR will equate to what true colors you see in sunlight vs the same object’s colors you see when illuminated with a flashlight. The closer the two are, the higher the TCR rating will be.”

The TCR Reference Standard is the Walmart Ozark Trail OT 50L , Model No. 6103.
It has a TCR rating of ‘10’. $1.00 including batteries.

BurningPlayd0h
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If I was to make a guess, while those LEDs still have a significant blue spike and overall different spectral makeup than a blackbody source the difference is insignificant compared to what a lower-Ra LED or florescent would have. The latter two have HUGE gaps in the spectrum that are underrepresented vs blackbodies. Since color of an object is determined by reflected light, the slight differences in intensity of some wavelengths doesn’t matter as much for accurate color representation (since much of the light is being absorbed anyway) vs a segment/segments of the spectrum being extremely low relative the others.

djozz
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About OP’s question: we do not see 450nm very well, our eyes are just 4% as sensitive to it as our peak at 555nm. So a spike at 450nm is not obvious. The blue is needed for natural colour perception, but the amount appears not very critical, although real snobs may see it.

Same for deep red, we hardly see it so it is not critical for how we perceive colours, but it does help for that last tiny bit of colour rendition.

In general: our machines detect light way better than our own detectors: our hopelessly primitive eyes. It must be noted though that we have brains that are extremely capable of squeezing every last bit of colour information out of our very poorly functioning eyes.

autumncrown
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djozz wrote:
About OP’s question: we do not see 450nm very well, our eyes are just 4% as sensitive to it as our peak at 555nm. So a spike at 450nm is not obvious. The blue is needed for natural colour perception, but the amount appears not very critical, although real snobs may see it.

Same for deep red, we hardly see it so it is not critical for how we perceive colours, but it does help for that last tiny bit of colour rendition.

In general: our machines detect light way better than our own detectors: our hopelessly primitive eyes. It must be noted though that we have brains that are extremely capable of squeezing every last bit of colour information out of our very poorly functioning eyes.

Lovely answer, thank you. Coming to flashlights as a bit of an objectivist audiophile, I know how controversial measurement of aesthetic machines can be. I would love to see the incandescent snobs defend their preference in a “blind” test.

I wonder if there will be any LEDs soon that fill in that last bit of red. Seems like sunlike do get rid of the blue spike.

djozz
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There is another reason to not want that blue spike, not colour rendition but the influence of blue light on our mood. There is some research on that, the effect may not be huge or worrying, and the definitive facts are not out there yet, but since it is picked up by public opinion as real and dangerous, led manufacturers have no other option than respond with leds that do not have that blue peak.

autumncrown
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Personally I have found blue blocking glasses to help me sleep and I know this is a fairly well validated fact. However for flashlights, because you can usually control the amount of light so easily, I don’t think it is as much of an issue. Also, IIRC, blue light impedes melatonin production but only if it enters the eye from above. So I drive my GF crazy by always using flashlights around the house before bedtime and turning off overhead lights.

djozz
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Light level is at least as important as spectrum in regard to sleep, in real life light levels (i.e. I dim my tablet to 25% in the evening, and the house is sparingly lighted) I wonder how much those glasses add to that, and how well the “blue light effect” is researched at those levels.

iamlucky13
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autumncrown wrote:
But is that why the r12 value is low? How can such a large deviation only result in a couple CRI points lost?

Only R1 through R8 are used in the CRI Ra score. R9 through R15 were added later due to recognition that fluorescent and other lighting sources with spiky spectra were not easily compared by Ra to sources with more continuous spectra.

Hence also why you can have R9 (saturated red) scores that are effectively 0, yet score well into the 70’s for Ra.

Specifically regarding R12 being low, scroll down to TCS12 here to see a reflectance spectrum for the test swatch:

https://www.waveformlighting.com/tech/cri-ra-test-color-samples-tcs

In short, blue-pumped LED’s have too narrow of a spectral peak to score get a great score here, as the test surface has significant reflectance extending into the violet range. To get a really good R12 score from an LED generally requires a violet-pumped LED like Nichia Optisolis. See here for example: Maukka’s 5000K Optisolis Measurements (source)

Fortunately, the typical LED scores in the R12 = 50 to 70 range keep the effect relatively subtle. Consider similarly how an R9 score above 50 is decent and above 70 is pretty good. Yet even before I understood the limitations of most LED’s at the blue end of the spectrum, I did notice this doing comparative photography tests of some of my first high CRI LED bulbs against some fluorescents. Although these specific CFL’s had a partially correctable color cast and had terrible rendering of greens, they actually did very well in the violet range. A vase of various colored flowers I used as a test subject showed the violet colors looking more blue and a bit dull.

Since I didn’t understand this at the time, I was confused that the high CRI bulb seemed to perform worse for shades of purple, but the improvements in the other colors compared to the CFL was far more significant.

As to the height of the spike, because most real surfaces reflect a fairly broad spectrum, we seem to not notice this. However, if you illuminated a surface with fairly narrow reflectance spectra centered on that same spike, the blue should appear exaggerated compared to when illuminated by sunlight.

autumncrown wrote:
Related question: How much does it matter that virtually no white LEDs have proper extension into the 700 nm+ range?

As far as I know, human eye sensitivity to 700+ nm is so low that it is almost irrelevant. It should be possible to create a test scenario with extremely low reflectance until nearly 700 nm where a difference would be seen compared to sunlight, for example, but I think uncommon.

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