DDD - Debris din Dome!

i examined the beams of my lights at a white wall, XPG, XML, whatever. in all cases the hotspot should be white in a uniform or radial symmetric way. we know that Cree LED's can produce a hotspot with a large darker circular center plus a very thin brighter hotspot ring. that's not nice but quite often the case and hardly noticeable. and not topic of concern.

swaying the lights, i did notice small dark speckles, maybe 1, 2 (or 3) of them in the hotspot area of some of my lights :shrug:. these seemingly randomly distributed but "fixed frame" speckles made the hotspot look ununiformly white and unclean. Okay, at max ("turbo") brightness they were less visible because of the sheer hotspot brightness blinding your eyes but white wall hunters and flashaholics could still see them.

Origin? Cause?

i always thought that the 1, 2 (or 3) speckles were a byproduct of the LED dye's parallel conductor lines until i examined the LED domes close-up with a loupe and a 1xAAA lighting source. Note, inspecting LED domes isnt a trivial thing because in most cases the LED is enclosed in the head in a sealed manner .. and the deeper the reflector is the harder it gets to make out anything conspicuous or extraordinary on or within the dome. So.. even if there was something in the dome, people with poor sight or lighting would not spot anything.

Let's take for example a Quark X. Large dye, deep reflector, sealed head. Typically no Quark user dares to unseal the 2-part head because it would void the 10yrs performance guarantee (warranty). (yes, the Quark head consists of two parts (screwed), you didnt know?)

Clearly, i detected a tiny impurity, some kind of dark (dust, dirt, debris) particle enclosed within the LED dome! oo: ... and i am sure it is not a loose particle on the dome which could be wiped off with a Q-tip. From what my eyes and the magnifying glass can tell, there is something in the dome!!

Not 4Sevens fault. It's sloppy and dirty manufacturing standards in CREE factories.
I found such dome-enclosed-particle in a few of my other XM-L lights too. I guess it is too hard and expensive to produce 100.0% flawlessly pure clean LED domes in a CREE factory! If you own a collection of 100 lights and their CREE domes are 100.0% free of 1 tiny (dust, dirt, debris) particle, then congrats, you won the jackpot :thumbsup:

Wondering now if i am the only one with dirty domes.. :ironic:
Next time i buy a new light and it hasnt a 100% uniform white hotspot area, i will inspect the dome with a loupe, and finally return the light .. because i wont accept DDD anymore.

Actually now that you mention it, I have also discovered exactly the same thing in my new Nitecore Explorer series EC1's. I have 4 of them and they all seem to have it. It looks a little bit like black pepper. I first noticed that there was some tiny shadows in the hot spots of their beams and so I decided to investigate a little further, and when I looked through the lenses with the lights turned off I could see the reflection of tiny black spots on the reflectors. I then had a look with a magnifying glass and I could tell that the spots were not actually on the reflector, and so I then had a closer look at them all by using a jeweller's loupe. They all appear to have these on the LED and just as I said before it sort of looks a little bit like grains of black pepper. I was extremely surprised that all 4 of them had the same thing, albeit in varying amounts and placement, but I can't really seem to tell if it is on the inside or the outside of the domes, however I very strongly suspect that they are all on the inside of the domes! I'm glad that I am not the only one that has discovered this because I have been wondering about it ever since I had originally seen them, and I also asked a couple of local dealers about it yet they didn't seem to know what I was talking about!

I also checked out several of my other lights (SureFire, Dereelight, JETBeam, Fenix, Sunwayman) but they did not have anything like it. Just a matter of interest though, whilst I was checking the LED's on some of my other lights, I did happen to discover that my new Sunwayman M10R has a really big smudge right in the middle of the dome, and it is so severe that I am quite certain that it would affect the performance quite dramatically. The best way that I could describe it is that it almost looks like it has been touched by someone that had glue on their finger and so it has left a sort of a glue fingerprint. I must say that I am not very impressed about it at all, however at least I will permanently have forensic proof of who is to blame!



P.S. I also checked my two Fire-Foxes 3's and my Polarion Abyss, however I couldn't even seem to find the LED's on them for some strange reason. Guess I need to get a more powerful loupe!!! :thinking:

Phil Ament said:

I have been wondering about it ever since I had originally seen them, and I also asked a
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big smudge right in the middle of the dome. The best way that I could describe it is that it almost looks like it has been touched by someone that had glue on their finger and so it has left a sort of a glue fingerprint.

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Yep, pepper. looks like that!!

Your SWM.. i believe to know what you are talking about. I've seen it on *brand-new* out of the factory lights. Have you ever personally fiddled with LED's and LED domes? Then you know that the domes have a dry shiny smooth soft jelly-like surface and when any object (like a Q-tip, grease, glue, finger, ..) touches it, the surface is altered and gets dull, less shiny. Smooth reflectors are the best way to spot such surface lesions because they magnify and enlarge the visible area. If a SMO reflector "looks imperfect" .. this may be due to LED surface lesions and not because the reflector itself has imperfections.

shelm said:

Yep, pepper. looks like that!!

Your SWM.. i believe to know what you are talking about. I've seen it on *brand-new* out of the factory lights. Have you ever personally fiddled with LED's and LED domes? Then you know that the domes have a dry shiny smooth soft jelly-like surface and when any object (like a Q-tip, grease, glue, finger, ..) touches it, the surface is altered and gets dull, less shiny. Smooth reflectors are the best way to spot such surface lesions because they magnify and enlarge the visible area. If a SMO reflector "looks imperfect" .. this may be due to LED surface lesions and not because the reflector itself has imperfections.

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No I have never personally fiddled with LED's, and about the closest that I have ever come to modifying them was to turn them on and off! Maybe I could have attempted to remove the pepper if I was a little more seasoned! :shakehead



P.S. By the way, what particular sort of LED is it that you linked to, and I presume that it has a really sweet hot spot. It does look so nice though that I feel that I could actually eat it!

Phil Ament said:

Maybe I could have attempted to remove the pepper if I was a little more seasoned! :shakehead
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and I presume that it has a really sweet hot spot. It does look so nice though that I feel that I could actually eat it!

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Phunny fill

( FYI, even an out of the box Q-tip can easily scratch/smudge the LED dome's outer surface. and yes, a single finger or finger print does the same. Never finger a hot pie or jelly pudding either! )

shelm said:

Phunny fill

( FYI, even an out of the box Q-tip can easily scratch/smudge the LED dome's outer surface. and yes, a single finger or finger print does the same. Never finger a hot pie or jelly pudding either! )

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Many thanks for all of the advice shelm and I will have to make a mental note about it all, especially the part about fingering a hot pie/jelly pudding as you may just have saved me from some serious injury, like a stroke for example. Thank you for the new Q-tip tip too. Wow, try saying that fast a few times!

A 'Pick Glass' is what I use to examine LEDs minutely. It's a specialty textiles manufacture tool. It's like a high-magnification loupe with a frame for use on flat surfaces - we use it to count yarns per inch in a weave. It also does a good job of seeing the LED in any reflector shorter than about 4cm deep.

I use a q-tip with alcohol on the led domes all the time. No scratches that i can see. Way better than leaving fingermarks No beampattern is 100% perfect. If you take your best light with the "best beam" and rotate it, you will see the "flaws".
Imo this is nitpicking. I cant even see the famous "cree rings" from the old xr-e in real world use, so I dont really bother looking for tiny flaws in a beam against a white wall.

jorn said:

Imo this is nitpicking.

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it's more like seasoning.
pepperpicking.

jorn said:

Imo this is nitpicking.

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shelm said:

it's more like seasoning.
pepperpicking.

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Hang on a minute. Shouldn't nitpicking be saved for the Niteye thread!

I don't think you are supposed to pick at nits in your eyes.

Also, I am curious now, about these pepper flakes. Are they square or are they round? Might they be bubbles? Are they arranged in any sort of pattern, i.e. are they all equidistant from the center point on the die, or maybe are they arranged in the same 2D plane? Even better, dare you to attempt to take a picture of it through a magnifying glass or aspheric lens. This is very curious, and to see Cree trying to get every last lumen out of the package but leaving little specs in the potting dome, doesn't seem right.

I'll have to take a closer look at my XM-L and XP-G. The rest of my Crees are glass domes, I think.

AnAppleSnail said:

A 'Pick Glass' is what I use to examine LEDs minutely. It's a specialty textiles manufacture tool. It's like a high-magnification loupe with a frame for use on flat surfaces - we use it to count yarns per inch in a weave. It also does a good job of seeing the LED in any reflector shorter than about 4cm deep.

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Maybe the most apt thing for discussing textile manufacturing would be a new thread! :shakehead I'm certain that we could have a good yarn or two!! :thumbsup:

Whatever it is, I have the same thing on one of my XP-G lights. In an otherwise perfect beam pattern, a faint, darker line near the middle of the hot spot and lo and behold, when viewing the LED dome, I can see that line across the dome (or inside it). It's also visible in photos of the lit LED. I wonder what it is.

i finally know where the speckles in the hotspot originate from!

they are only visible in XM-L white wall beamshots, not in XP-G white wall beamshots.

basically the speckles are (the remains of) the projection of the XM-L conductive paths (strip lines) at the bottom of the dye. since the lines are darker than the green-yellow dye of the CREE led, they project as trace remains on a white wall. what we see looks like dark spots or points on the wall .. but you need to rotate the beam profile slowly to realize that the points are only parts of the whole. connect the points and you'll get the conductive grid of the XM-L led.

mystery solved.

A couple of my Quarks actually have "a tiny scratch on the dome of the emitter" Cant notice anything in the beam, but very annoying. I tried to disassemble one of my quark heads with no luck and just ended up scratching the anodizing. (rubber band technique)

Hi

tickled said:

Whatever it is, I have the same thing on one of my XP-G lights. In an otherwise perfect beam pattern, a faint, darker line near the middle of the hot spot and lo and behold, when viewing the LED dome, I can see that line across the dome (or inside it). It's also visible in photos of the lit LED. I wonder what it is.

Click to expand...

I found a similar problem on my new Sunwayman V11R, wondering if I should see if I can get it swapped. I'm sure I can learn to live with it....But I know it's there.:hairpull: Puts a little damper on the excitement of a new light

No obvious changes in the beam pattern.

(Dedome later down the line? :/ )
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