Here’s a list of light bulbs, sorted by CRI_Grades. The bold are light bulbs you could use in your home. The CRI_Grade is meant to be read just like a school test score.
This grade is calculated by a math formula. I’m really loving the grade results vs what I think about them after reviewing all the color data from my spectrometer.
And my God, those SunLike are the only LED technology to earn an A grade. Not only that, the SOL model beat the sun itself (If you are wondering how, the sun’s not so perfect after it comes through the atmosphere.)
I wasn’t able to find the CRI data for those. But Ra and R9 are stated to be 95. That would seem like a good start, but by looking at the TM-30 diagram, it seems other colors are lacking.
But if you like them they can’t be too bad.
Would you mind elaborate how you classify the grades from A - F?
In my book:
I will give most R8000 lights a ‘D’ (plus/minus depending on tints), the bare minimum people should ever be consider using. Obviously R70 and below will invariably get a big fat ‘F’ from me <span class=““eww” muffled a with”>.
R9050 will be given a ‘C’, the bare minimum I will seek out to use for myself if they are cheap.
“Royal Blue” based R9080s will be given a ‘B’, an upgrade over R9050 but the blue peak and the violet/cyan intensity gap still concerns me a bit.
The likes of SunLike/Optisolis will get a solid ‘A’ from me.
I gave some thought to posting the formula for my grading scale in the OP. It sure isn’t worthy of being a secret or anything, I just didn’t want to debate it. It is quite hard for LEDs to score good on it. For example, the Optisolis E21A running at 2A without a reflector scored a C+ in the OP. I will post the data below. You will see the R9 and R12 were only 80, and I put strong emphasis on them. So this would be a R9080, scoring a C+.
I don’t even know what LM79 is. As noted in the OP, the ones that have a * by them were not tested by me.
After seeing this table though, I did place an order for a SunLike bulb. It’s just curiosity for me though, as the 6w cost me $22 for a single bulb. Each room of my house requires 4 or 5 bulbs.
You’ve probably seem me recommending Hyperikon in a few threads. This isn’t because their performance is perfect, it isn’t, it’s because their performance vs price is unbeaten.
I’m back.
Ok. So CRI_Grade. The convention of marking “R9080” to mean Ra=90 and R9=80 works pretty good as a judge of CRI quality. With today’s tech, R9 is the hardest to achieve, and that puts it in plain view. However, some manufacturers now know how to trade R12 for R9. This means R12 could be the only one that is super low and go unnoticed. Now, I’m also a believer in simplifying things, so this is what I did…
I marked my readings, for example, R908060 (Ra=90, R9=80, R12=60). Then I just averaged those numbers. In this example, the answer is 76.66. This gives great importance to the weakest areas of LED technology, resulting in a super useful number. But grading still needs to be done, otherwise it’s not simple enough. So I just applied my High School’s grading system. This specifically calls for rounding to the nearest whole number, then categorizing. (Grade table in spreadsheet). So in this example, 77 = D+.
To see the formulas, grading scale, and to play with your own numbers, download my spreadsheet here
Now if you can read a data dump from a spectrometer, this obviously has less information. But as a muggle, this is like having that data dump read for you. And it focuses on the hardest parts of making an LED, so if the manufacturer gets this right, it’s doubtful they could AND would screw anything else up too bad.
Except for Duv and angular tint shift, both of which are extremely important and noticeable.
Edit to add: I don’t think I’ve ever seen bad tint shift in a household bulb because they’re generally quite diffuse, but it’s common in flashlights. Look at the beam from a flip-chip Cree like XP-G3 or XP-L2 in a reflector and see all the rainbow colors.
Duv is harder for companies to keep under control. Because our vision is so sensitive to green light, adding just a bit of green can bump the lumens way up without wrecking CRI, in order to recapture some of the efficiency penalty you normally find with high-CRI LEDs. But doing this also gives the light a green tone (a positive Duv), which deeply annoys a lot of people.
I don’t want to say CRI_Grade is anything more than a color rendering score… But at these strict of levels, I don’t know of any real life bulbs that would have bad Duv or tint shift while scoring good on CRI_Grade.
About CRI rendering: recently, I started to appreciate the newest CRI measuring method, which uses two values to present overall CRI. Rf (fidelity) is very similar in meaning to Ra (I won’t try to research for the differences now), and the other value is Rg (gamut), which tells, that how much the examined light source is greenish/yellowish (values under 100) or rosy (values above 100).
Rf measures as the same as Ra (range 0-100).
Rg measures from (100 minus Rg’) to (100 plus Rg’), where Rg’ = 100 - Rf
I would use a starting formula something like this:
0.7 × (Rf / 100) × Rf + 0.7 × ((100 - Rf) / 100) × Rg’’ + 0.15 × R9 + 0.15 × R12
Rg’’ is calculated like this: 100 - (abs(100 - Rg) * (100 / Rg’)) - this tells us, how much the light source deviates from the black body line, if compared with other light sources having the same Rf.
So, for example, if an emitter with Rf=90, has an Rg of 93 (could be called very dull or greenish) or 107 (could be called very ill or rosy), has an Rg’’ score of only 30, while light source spot on BBL would have Rg’’ = 100.
The first two Rf based coefficients corrects for the cases, where e.g. Rf = 98 and Rg = 102 -> that is definitely not a bad light source, which would deserve Rg’’ of 0.
Edit: Please ignore above anything I said related to Rg, as of maukka’s clarification.
Speed and simplicity would be the advantage. Can you imagine if I posted all 41 of the TM-30 (or CQS) diagrams and your job was to spot the best ones? Or sort them?
(If you are wondering how, the sun’s not so perfect after it comes through the atmosphere.)
Ok. I’ll discuss my CRI_Grade calculation when I get back to the computer around noon.