White vs High CRI

OP here

what i consider a good white, is usually rated 3500-4000K

should that be high CRI, or not?

i guess what i don;t get is, why are the ‘other colors’ necessary, since our eyes only respond to 3 broad peaks of wavelength?

since white has all colors, if something appears white, why would it not be ok for the human eye to see all the colors the eye can see (which isn;t many)?

does a 100-CRI light appear to be a perfect white, or something else?

an emitter producing light exactly matching the wavelengths your eyes respond to in correct proportion would produce a perceptually perfect white light but I believe the light reflected back from objects you shine it on could look strange and “wrong”

if you want to see examples of 100 CRI light just look at any clear glass incandescent or halogen light or unobscured sunlight. they can appear to be “perfect white” depending on context. perception is subjective.

CRI is for vibrancy and colour accuracy.
Kelvin is for warm or cool temperature. Basically a level of whiteness from yellow to pure white to blue.
Natural white light is somewhere around 4500k.

If you point your 2700k High CRI flashlight at a red object, you’ll without a doubt know that it’s red.
It will have a warm tint to it, but you can clearly tell it’s red. It won’t look orange, pink, maroon, yellow, or anything else but red.

If you point your 2700k low CRI flashlight at the same object, not only will you have a very warm tint but you won’t be able to accurately identify colours.

They are not mutually exclusive. You can have high or low CRI with warm or cool temperature. It’s just more common to see it with warmer tint.

I believe you are talking about the difference between emitted and reflected light.

A source that you look at directly, like a TV screen, can get away with emitting only three wavelengths because you are looking directly at them. It can mix those three colors to trick your brain into thinking it’s seeing an intermediate wavelength. However, when light reflects off an object, it may not reflect 650nm and 530nm light the same way it would reflect, say, 580nm light. If a source only emits three individual wavelengths, objects will appear to have strange and altered coloration when viewed in the reflected light from said source.

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
.
(guess which is which)

extra credit quiz
which one tastes Redder? LOL