# Quantifying color rendering quality



## Canuke (Oct 9, 2014)

Hello CPF,

As most of you reading this know, one of the most prominent issues we focus on here is color rendering quality (CRQ, the general concept which CRI is one attempt to measure), especially for lighting in the home.

In my case, while I know all about CRQ, for the most part I find myself seeing very little difference between any sources of CRI 80 or higher, in ordinary use. I'll see someone here favoring this source while knocking another, or swearing up and down about the virtues of the Nichia 219. I have two of those and a warm HCRI Preon, and when I compare to non-HCRI warms, I don't see the difference , at least with ordinary household objects I have lying around.

There has only been one exception that I've found hard to duplicate: I have had in the past a dessert wine, icewine, made from cabernet franc grapes, and it has a signature orange-ish red color. Seen in incandescent light, it's red, thinning to orange. In any other warm white source, be it CFL or LED, the color changes; it's noticeably duller and more brick colored. Since it's deep red that is the biggest thing missing from "incandescent fakers" versus the original, that makes sense to me. That icewine is, alas, expensive - too expensive (and delicious) to sit around as CRQ test equipment.

So what I'm asking the CRI aficionadoes here, is what objects are you looking at when you notice "bad" CRQ? I'm looking for things that are sufficiently consistent across examples that I could go find one and see the same thing you do, given the same source. Going further, that might be something that reviewers could use, standardized reference objects that allow them to check the CRQ of a source in a quantifiable way.


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## 880arm (Oct 10, 2014)

Although two LEDs may be rated with the same CRI, it doesn't mean they have the same spectral distribution. One may do a better job with the blue-green part of the spectrum while another may be better suited for reds or browns. 

For me the best way to tell a difference is to illuminate some objects that are very similar in color but not exactly the same. The lights with better color rendering will do a better job of highlighting the subtle differences. When outdoors this might be grass that is a slightly different shade of green than the surrounding foliage, or something like creek gravel which has lots of different shades of red, orange, and brown. When indoors, a row of books or maybe some wallpapers will work well.

I remember someone on here mentioning they use their high CRI light to distinguish between black and dark brown socks. I haven't tried it myself but that seems like a pretty good test as well.


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## Cataract (Oct 26, 2014)

I use color charts when picking a filter to correct color rendering on my 5000K+ flashlights. Two printers will not print the same color chart exactly the same, but I have been able to pick filters that convinced just about every other CPF member who have seen the result of using a color filter to imitate a high CRI emitter from a simple 5000-6000K cool emitter. 

I guess using a color chart made of CMYK percentages for each slice or square and having that printed by a photo-quality professional printer could do the job.


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## KITROBASKIN (Oct 26, 2014)

Here in the high altitude, semi-arid southwest, the everywhere-around-you, light/medium brown soil color is a challenge to render well, with the non-HiCRI XML series, domed and dedomed, being problematic. The Nichia 219A makes the soil look 'too pretty, too rich', while the Luxeon T seems to be the least distracting to me.

Having not seen a very important difference in primary colors as well as the different blends of shades, the quick-and-dirty solution indoors for me has been standard, brown cardboard boxes. The various shades of light and medium wood furniture can also reveal the excess yellows and greens found in Cree LED's. I have no experience with their HiCRI offerings.

It sounds like you are satisfied with your lights, and you just want to see what people are talking about, or are wondering why folks only want HiCRI emitters. Hopefully you won't get caught up in that scene. To me, the bottom line is that, in the field, the illumination is not drawing attention to itself, and that what you are looking at, is what you are looking at, instead of the quality of the color rendering.


Sent from my iPad using Candlepowerforums


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## Anders Hoveland (Nov 29, 2014)

Canuke said:


> I find myself seeing very little difference between any sources of CRI 80 or higher, in ordinary use.


Many people will likely not notice, at least not consciously. CRI of 85 is usually considered "good enough". Some people are just pickier, and either want better quality of light or just want colors to look exactly how they should.

I can notice the difference between 85CRI and 95CRI just be looking at the light from the lamp— on a white surface. Standard 3000K LED light has somewhat of a yellowish tint, whereas 3000K 95CRI LED light has an orange-tinted, more natural white light. Skin tones look greyish and a little yellow under 85CRI LED, but is bright and the right color with 95CRI. 

The difference between 85CRI and 92CRI is a little more subtle, but it is noticeable. Warm colors appear just a little more "full", and the surroundings tend to appear just a little more colorful.

The light quality really starts to improve when blue LED phosphors are used (violet emitter). I have a 5000K 97CRI violet emitter white LED, and the light it gives off does not feel like "LED light" at all.

What I am trying to say is that if you go from 85 to 92cri, or 92 to 95cri, you might not really notice anything, but if you go from 80 to 97cri the difference will be much more obvious.




Canuke said:


> So what I'm asking the CRI aficionadoes here, is what objects are you looking at when you notice "bad" CRQ?


Typically the big thing is red rendering, just as you have observed. Sometimes forest greens can be rendered just a little yellowish green under LED light.
But by the time you get to 95CRI, the LED already has all the red color rendering it is ever going to have. Above that, it is more about the cyan and blue.


Also I want to emphasize that the Color Rendering Index is not a true measure of the quality of light (how it feels), but yes, typically the quality of light tends to be better at higher CRI. CRI is can be used as a general indicator of quality of light, but it should be remembered that CRI only attempts to be exactly what it says: an index of how well the colors of different objects are rendered, nothing more.


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