So
What is the relation between ‘’high CRI’’, and “that light color looks perfectly white to me”?
Is it possible to just have one of those 2 things, more of one than the other, or are they basically the same thing?
Seriously
I have some LED bulbs that appear to me as perfectly balanced, white light.
Yet I think of “high CRI” as “expensive”, and I have never paid over $3 for an LED bulb.
wle
There is basically no correlation between color rendering and whiteness.
Consider this web page: BLF is mostly just white. That is produced by your computer screen using just three monochromatic colors: Red, green , and blue. The three of these together can produce “white”, while being extremely low-CRI - try comparing light from a phone or computer screen to a white LED and you will see this in action.
CRI - the color accuracy of light as compared to a “black body” emissions source (like an incandescent lamp or the sun), where a black body source is 100 CRI. A low CRI light will not show certain colors accurately or brightly.
color temperature - the amount of yellow-orange or blue visible in the light source measured in Kelvin. a 60W incandescent lamp heats up to approximately 2700K, thus the color temperature of the light it produces we call 2700K. this light is considered “warm” though the number in Kelvin is rather low. a Xenon arc lamp glows at around 6200K producing a blueish light quite similar to daylight at noon, and we call this “cool” despite its higher Kelvin temperature value.
tint - a measure of the “greenness” or “rosiness” of the light. perfect tint appears neither green nor magenta and is exactly aligned to the black body locus (see below) whereas green tint (often seen as undesirable here) is any point above the line and rosy tint (sometimes desired here) is below the line
If you want a “perfectly balanced” white light, you may not need high CRI depending on what you are looking at. But if you want colors to “pop” and be rendered accurately as if in sunlight, you’ll want a higher CRI. You’ll almost certainly want a light with “perfect” tint as close to the black body locus as possible, and your preference for color temperature will depend on context—where are you using the light and what color temperature will your eyes be adjusted to? 4500k is a good medium value, but if you are using it outside near 1700K low pressure sodium street lights it will look quite cool and if you are exiting your kitchen where you have installed 6500k cool white bulbs it will look warm. If it is the only light source, your eyes will tend to adjust and the color temperature you see will look pure white.
Yep, there is no correlation and maybe negative correlation depending on your definition of “white.” It sounds like your definition of “white” is a high color temperature above 5000k. On the other hand, lower color temperature lights look “yellow” and tend to have higher CRI. This is because the red part of the spectrum is the most inefficient to produce and lower color temperature lights need less red to be close to the black body line.
People on here and Reddit especially try to chase high CRI but sacrifice too much in color temperature in my opinion. I’ll take high CRI, high color temperature over the same CRI but low color temperature any day. You have more color separation at high color temperature if CRI is constant.
Another way to say this is that 100 CRI at 1800k will still make everything look yellow-orange. Or a more extreme example is 100 CRI peaking in the infrared will make everything invisible.
I don’t think low CCT is a “sacrifice” so much as a preference. I prefer warmer temps because I think cooler temps make things look cold and sterile. I’d rather have a 3500K 80 CRI than a 6000K 90 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.
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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