Using UV to separate Cool White LEDs from Neutral and Warm LEDs

natural daylight:


UV light:

That will work for quite a few LEDs but I have quite a few LEDs where they are the exception. Yugi for example, I have some 2500k & 3000k that look almost green under uv, and some cool whites that are very orange in uv light.

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You might try a blue LED instead since the phosphor is designed to react to blue not uv

FRITZHID said:

they are the exception. Yugi for example, I have some 2500k & 3000k that look almost green under uv, and some cool whites that are very orange in uv light.

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excellent point, Yuji 5mm LEDs respond essentially the opposite way that cree and nichia surface mounted chips do under UV




we can still use UV to tell the 5mm warm Yuji and cool Yuji apart, the cool white Yuji glow red
with Cree and Nichia chip LEDs, the neutral and warm ones glow orange, the cool ones glow greenish yellow
the Nichia GS cool white in the Fenix E01 also looks greenish yellow under uv

🤔
Very interesting. I d like to learn about this

you are always up to something Jonathan.

this gives me a new reason to play with my uv lights

Thanks for starting this thread; it will definitely be a learning experience for me as well.

EDIT: okay Jonathan; I have one for you.

most neutral/warm emitters glow warm.

seoul p4 cool white glows green

cool whites glow blue

Kicker...Malkoff M61T 6200k cool white glows warm. This light has a TIR optic; so i don't know if that has anything to do with it. I only have approx 15 lights in front of me; rest are downstairs. I have an M61HOT which is TIR as well. i will have to check that one.

another Malkoff module i found is the M91B cool white (6200k XP-L) which glows warm. no TIR just reflector and emitter.

otherwise it's accurate and a little bit of fun. at some point I will check other lights.

@INFRNL thanks for the additonal info on other LED models and their colors

we obviously have too much time on our hands, and too many lights... LOL

I was looking at a 9 pound pile of 47s parts that Im sorting for a friend, to reduce the shipping cost overseas.. at first I was sorting by the color of the heads under natural light (most are without bodies, so turning them on was not an option).

then I double checked with UV and found a few more that glowed warm, the UV made the sorting easier.

fwiw, all the lights I was sorting have reflectors w glass lenses

after reflecting on your mention of TIR I decided to test some of my TIR lights, and it turns out that some of them dont let the warm color of a sw45 N219b show up. It seems 3 out of 4 of my Tir block UV, while it seems the glass lenses allow the UV to show the warm glow of my High CRI Neutral and Warm LEDS

all these lights have High CRI LEDs, but only two seem to allow UV to pass

I was wondering what you were doing with all of those heads. I can see where the UV would make it easier and quicker. i would have never even though until you made this thread.

yeah, late nights on the forums with nothing but time to kill before i finally get tired

Hi Jonathan,

a really great idea! In the past (that means in my case a few years ago) I was searching my warm white lights exactly this way. This works perfectly for let say older LEDs like SSC P4, XP-G, XR-E, …. But I forgot this fact. Yeah I am getting old…

Today I I was reading this thread I made an "marker" and I was testing my Nichia 219B and 219C HiCRI and Ultra HICRI Lights with my HDS UV Light. The interesting fact. I was not able to see a difference between NB35, NB40, NB45, and also no able to se a difference between NC27, NC30, NC35, NC40, NC50 and also NC57. All of this LEDs were glowing in basically the same orange.
I assume the reason is the phoshpor (or whatever they use for the HiCRI LEDs) glows more or less the same no matter what light Color.

But I still like the idea on selecting the light Color using UV light. I am sure for older LEDs it is working perfectly.

WarriorOfLight said:

... I was not able to see a difference between NB35, NB40, NB45...

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I agree and have the same experience, I cannot determine the color temperature of my High CRI lights using UV, I can only see that they glow orange (and only if they are under glass, not if they are under TIR, with one exception)

I dont know what material different TIR are made of, but I do know that polycarbonate blocks UV..

separate from UV
the way I can get an idea of the Color Temperature of my lights (no matter if high cri or not) is to shine the lights on my white ceiling, next to my incandescent light. With that technique I can sort my LEDs in ascending order... 3000k LED, 3500k, 4000k, etc

for example, I have found that two of the XPG lights in the big group of heads are not the same CCT, one is 3000k, the other is 3700k.

Im not saying shining on the ceiling tells me the actual CCT, but it gives me the ability to look up the different lights specs, to confirm which one is named by the MFG as 3000k or 3700k in that particular model line.

I can do similar CCT sorting by using one of my known 3000k lights, and one of my known Cool White lights, and then arrange other lights between those two references. Again, not a perfect tell of the actual CCT, but a good approximation of the relative progression of coolness or warmth..

not all my 3000k LEDs for example are exactly the same tint, but I find the 3000k 219c and 3000k XPG look very similar to each other, and to the incandescent.

interesting....another new experiment to try. I only shined the uv directly at the led; will have to try bouncing it off the ceiling.

INFRNL said:

interesting....another new experiment to try. I only shined the uv directly at the led; will have to try bouncing it off the ceiling.

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thats not what I meant! but go for it

public service announcement
warning, protect your eyes from UV
I consciously rely on my polycarbonate lenses, which I tested and confirmed actually do block the UV from my flashlight
even cheap safety glasses block UV, they dont need to be yellow.. just use Protection if youre going to screw around, with UV.. we would not want anyone to mess their eyes up doing this stuff

Respect UV, it is not a toy, do not expose your naked eyes to uv, not even reflected backscatter.. its dangerous, be careful
end public service announcement

jon_slider said:

natural daylight:

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First, that's a neat idea, but most importantly, man, that's a LOT of flashlights : )

Derek Dean said:

man, that's a LOT of flashlights : )

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yes, about 10 complete lights.. lol
I had never handled any quarks, they have some very complex features.
Notably the 8 mode options... tight head and loose head toggle from Hi/strobe to moon/low/med/higher/strobe/beacon
enough to drive me nuts!
imagine how a muggle would feel..

there were also flush tails, raised buttons, momentary forward clickys.. oh my spinning head!

my favorite was a little Q123 3 mode twisty w 3000k XPG, until I saw its constant flicker in a photo:

and a cute little AA twisty, that unfortunately did not seem to work

I think it was all stuff from customer returns.. some of it worked fine, my guess some of the customers just got lost trying to understand the UI

It kept me entertained for a few days.. learning what it was all about.. then I forwarded half of it to the overseas owner, and gave the rest away..

Im still in my Jetbeam rotary phase.. multy mode clickies are so, yesterday.. for me.. lol

Interesting use for UV. What wavelength is that UV flashlight?

PhotonWrangler said:

Interesting use for UV. What wavelength is that UV flashlight?

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it is a true 365nm
this light:
http://www.candlepowerforums.com/vb/showthread.php?428230-Jetbeam-Jet-UV-Review

not the 395nm version used in the Tube
https://www.candlepowerforums.com/vb/showthread.php?423411-Nitecore-tube-UV

Do you have a UV light, and what do you use it for?
I dont hunt scorpions, we dont have those here.

I use my UV to test US $100 bills, to make sure they are not counterfeit, before I go grocery shopping.
I would hate not to be able to buy my groceries, because of fake money.
I have never found a fake, fortunately.

jon_slider said:

it is a true 365nm
this light:
http://www.candlepowerforums.com/vb/showthread.php?428230-Jetbeam-Jet-UV-Review

not the 395nm version used in the Tube
https://www.candlepowerforums.com/vb/showthread.php?423411-Nitecore-tube-UV

Do you have a UV light, and what do you use it for?
I dont hunt scorpions, we dont have those here.

I use my UV to test US $100 bills, to make sure they are not counterfeit, before I go grocery shopping.
I would hate not to be able to buy my groceries, because of fake money.
I have never found a fake, fortunately.

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Ahh, a true 365nm light; good.

It's interesting how different phosphor blends react to UV. Some of them will glow different colors depending on whether it's UVA or UVC excitation; I've seen this in my fluorescent mineral collecting hobby. Along these lines, they might glow with a slightly different color when excited by blue rather than UV light, since most phosphor blends are tuned for blue.