that doesn’t sound right
but it’s original, at least!
WHAT!WHY?
So essentially, Hi-CRI is not bound to a specific color temperature, but to a range usually below 5000k?
When a temperature rating is stated for a given emitter, that’s the emitted light, not the temp that will be reflected?
Consider temperature to be totally independent from CRI. An 1800K sodium vapor street lamp is very slow CRI (notice that you cannot easily distinguish colors by this light) whereas a candle at that same color temperature is very high CRI. Likewise there are (a few) 6500k >90 CRI emitters and many with very poor CRI.
Temperature measures essentially the ratio of yellow-orange to blue light you perceive. CRI measures the rendering of each individual color. This image comparing a high CRI (left) and low CRI (right) light source may help
Warmer color temperatures will have a peak further to the right, cooler will have a peak further to the left. This is independent of the overall shape/smoothness/completeness of the spectrum which is more or less what CRI measures.
Nothing original about it. Ever try to illuminate a room with an RGB LED?
To me, perfectly white means sunlight at midday which is 5700K.
And then for high CRI you need to find LEDs that have high CRI at that CCT.
For me, I have a flashlight that has quad Nichia E17A SM573-B12-R9080 5700K LEDs that seems to fit your criteria.
Our vision adapts, and so there’s a broad region in the spectrum we can perceive as white. In the presence of two light sources, the reflection of one will appear white and the other not. If pointed to a white wall only, one light source appears rosy and the other greenish.
One easy way to learn about high CRI LED lights is to get your hands on a one (a bulb or flashlight), and shine it on some light colored wood furniture or flooring. Oak is a good choice.
Then compare against a low CRI light with the same Kelvin rating.
The difference is easy to see, and will probably surprise you. It sure surprised me. That's why I pay the extra bucks for high CRI.
For most rooms in my house, I use "neutral" 5000K bulbs, but, as you can see from the posts here, many folks prefer something warmer. Once again, you gotta try 'em to find out what you like.
I’m always perplexed at people that ask a question about something they admit they don’t know about (implicit and explicitly), and THEN come back at people providing answers with attitude and dismissing / discrediting the information.
Rayoui is correct, as are others here. Maybe in the situation where you don’t understand an answer, you could try asking a follow up question or for clarification instead of dismissing folks.
There are many layers to this topic, and a requirement of nuanced thought/understanding of the interdependent variables. Absorption, reflection, and emission are maybe terms to research and gain understanding of before continuing here.
1 Thank
Very interesting replies. I am still trying to fully understand it. Maybe someone can explain this. I build / mod mostly throwers for fun.
I had a MF04 with a XHP 70.2 P2 1A 6500K ( 70 CRI ) that burned up, so I replaced it with a XHP 70.2 N4 5000K ( 80 CRI ). I was pleasantly surprised at the down stream visibility increase because the reflection was less and this helped to see clearly. Lumens appeared less but I think it was because there was less reflection. Is this true ?
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@CNC, was the reflected light maybe causing a glare or wash-out that distorted your vision, and with “less reflection” the long distance viewing was clearer?
The whole idea of CRI is related to how well you can see the true colors, like if you spotted someone walking out at a distance was their jacket brown, black or navy blue.
The temperature in Kelvins is related to the overall average tint color of the light, with the higher numbers toward blue-white and the lower kelvins toward orange-red.
It’s hard for me to see the real colors of things when the light is biased toward red, could be worn out eyeballs…
[edit] improper use of the technical meaning of “tint”
fwiw, Tint is not the same as Color Temperature
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and white is not just one Color Temperature, warm white is 3000K and lower… Cool White is 5000K and higher… 4000K is Neutral White
Neutral Tint is not the same as Neutral White…
Neutral Tint is actually all along the Color Temperature line, neither green, nor magenta
there is a LOT more info on Color Temperature and CRI, in this thread, includes photos… scroll down to posts by BrokenRecordBot
I'll try to dumb it down a bit. If you mix red, green and blue light, you get white. So far so good. Imagine an object which only reflects yellow light, but no red and green. In sunlight this object will look yellow.
But in the RGB mixed light it would look dark and dull, because there's no yellow light to be reflected back.
Maybe, depending on the actual spectral reflectance of the object, it might even appear more orange or more greenish than it would be under sunlight, even if the RGB light source looks exactly like sunlight to your eyes. This is the effect of low CRI.
This is also true if you compare a high CRI and low CRI lightsource. They can have the same CCT (color temperature, for example 2700K for incandescent) and tint (green/magenta shift, pretty much perfectly neutral for incandescent) and look exactly the same to your eyes on a "perfectly white" surface, but once you introduce real world colors (inks, pigments etc.) the colors you see will be different.
I’ve seen lower numbers than that quoted. But it’s not entirely relevant. How often do you hold your flashlight directly overhead pointing straight down? How do you like that midday sun when the ground is covered in snow? When you’re holding a flashlight at night and light is reflecting back at you off of trees and or other surfaces that’s a whole lot different than the sun being straight over your head. Cooler temperatures including 5000k and above are going to reflect more light back at you off of objects than warmer temperatures. That affects your ability to see past the close objects in your light path. So we can’t compare the big flashlight in the sky to the little one in your hand.
Excellent Post!
one of the very best, explanations I have seen
Happy Holidays!
> But in the RGB mixed light it would look dark and dull, because there’s no yellow light to be reflected back
same thing happens with Red, and this is The BIGGEST difference between Low CRI and High CRI:
things that reflect red, will look Red, only if the LED produces Red, which Low CRI does not
if the light is Low CRI with Negative Red output, then the red object will look brown
here is one example:
High CRI and Low CRI Tomato sauce
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(guess which is which)
extra credit quiz
which one tastes Redder? LOL
Very useful info from Jon Slider. I tend to agree with most of what he has to say. I’ve learned a bunch from his posts over the years.
One minor difference between him and me (which we have discussed in pms) is that I go with the photographer’s perspective on what makes neutral white.
Take a look at the image above. If you draw an oval around the white central region, I want to be on the black-body radiation line right in the middle of the white area. Roughly speaking, that puts me somewhere between the dot at 4000K and the dot at 6500K, closer to 5000K than 4000K.
sounds like the Higher CRI helped create better color separation… imagine how much better it could get with a 90+ CRI LED 
have some fun with this Low CRI vs High CRI comparator:
https://techneesh.com/assets/juxt/cri1.html
I think the perception that you must sacrifice “white” to get “high CRI” comes in part from the available selection of LEDs.
- Many people think of “white” as “cool white”. This is a misconception. A color that looks pure white under one lighting condition may look too warm or too cool in another. Human eyes have an auto-white balance which tends to correct for color temperature, to an extent.
- Most high CRI leds were only available in warmer color temperatures. This is true for XPG, XPG2, SST-20, XPL-HI. Nichia 219B at 4500K is a bit of an outlier on the cooler side, but has low output.
- It is only recently that high-CRI has become commonly available in some cooler tints. LH351D at 5,000K for example. But even then, these high-CRI LEDs tend not to be perfect, often featuring a greenish tint.
- Result is some people associate “high CRI” with “not white LED”. This despite the fact that color temperature and tint (which together determine how white an LED appears), are separate factors from CRI.
@jon_slider regarding the tomatoe sauce - I thought red was more to do with R9 which is not part cri calculations…?
I thought R9 is part of CRI calculations.
It’s just that CRI is calculated based on the average score for a whole range of colors, including R9. If all the other colors score high and R9 scores low, an LED may still rate as high-CRI, because the average is high. However, without R9, reds will still look washed out or the wrong color.
I think this is why the top-rated leds for CRI on BLF are typically also the ones with decent R9: SST-20 and Nichia 219B.
EDIT: see Luxwad’s explanation in post 31. My explanation in this post is wrong.