L4's 5 watt Luxeon dark spot...

L4\'s 5 watt Luxeon dark spot...

I had a buddy install a 3 watt Luxeon emitter in the bezel of my SureFire L1. The output is white and without any dark area in the hotspot. On the other hand, I just received an L4 which is almost as white as the other light, but it has a slightly noticeable dark area in the hotspot. I saw other L4s, and they are all the same.

If the L1 had a reflector instead of an optic, then would I see a dark area as well?

If the L4 had an optic instead of a reflector, then would the dark area disappear? What causes the dark area to appear, and why is it tinted yellow on my L4?

Re: L4\'s 5 watt Luxeon dark spot...

The 5W LS is made of 4 1W emitters arranged in a square pattern. Because of this, no light is emitted in the middle of the 5W LS. But this 'problem' can definitely be addressed by correctly placing the LS in an appropriate reflector. I have seen quite a number of L4s, and while most of them have the donut hole, there are some that are absolutely perfect. It's a matter of perfect placement of the LS in the reflector.

Re: L4\'s 5 watt Luxeon dark spot...

Thank you for your speedy reply, Mark2. I seem to remember reading this somewhere, and it makes sense. The L4 is my first 5 watt Luxeon light, so I am slowly learning about it's characteristics. You are writing about a front/back adjustment, correct? Is there any way that I can adjust it in the reflector?

Re: L4\'s 5 watt Luxeon dark spot...

Mark2,

Is the item on this Luxeon website the one in my L4?... http://www.luxeonstar.com/item.php?id=378&link_str=67::85&partno=LXHL-LW6C

Re: L4\'s 5 watt Luxeon dark spot...

I beg to differ a bit here. I believe the dark spot in the center of a 5W LED and reflector comes about when the reflector accurately focuses the image of the 5W's die. On a smooth, sharper focused reflector setup, the "null" will be most apparent. If you were to draw a circle around the square die of the 5W that was tangent to the four corners of the die, this circle will contain four outer sections where none of the die is present. These sections are seperated by corners of the die. Now if you draw another concentric circle that is tangent to the sides of the square die and consider the region between the two circles, I believe you are looking at the source of the "null". I believe the outer area of the die is projected to the inner section of the beam. Because this outer section contains an area from which no light is emanating, its density of illumination is less than that of the interior of the die.

At any rate this is my understanding but I have not demonstrated to myself the proof of this. I do know that the solution toremoval of the null is to either use a reflector which has texture for "blend" or move the die rearward of the focal pointof thereflector or both. The 1W ot Lux III also has a square image but I believe its relative smaller size results in a beam less indicative of having a null. It may be that the smaller die allows for easier de focus of the die in the reflector?

The 5W's in larger diameter reflectors are easier to manage in terms of the "null". I presume this is due to the relative size issue. /ubbthreads/images/graemlins/icon3.gif

I also suspect that there are some CPF members who actually understand the physics involved and they could step forward and provide an accurate explaination, should they choose to do so! How about it guys??? /ubbthreads/images/graemlins/tongue.gif

Re: L4\'s 5 watt Luxeon dark spot...

I don't know nothin' 'bout no physics, but when I hold my L4 within 2 inches of a wall I can see the unlighted "+" where the four dies meet. As I move the light closer to the wall this "+" becomes more distinct.

Re: L4\'s 5 watt Luxeon dark spot...

Are you out of breath Don? Do you need oxygen? What a mouthful of very useful information. I can honestly say that this is the first time I have received such a complete explanation of Luxeon dynamics. I very much appreciate it. Now I can really understand why the different wattage Luxeons perform as they do.

Is there any relationship between the tint of a KL4 bezel and the amount of light emitted? Would a bezel with a white output emit the same amount of light as a bezel with a slightly yellow tint?

I also welcome anybody who has more to add to Don's testimony, to stand up and be counted. I appreciate all the help I can get.

Re: L4\'s 5 watt Luxeon dark spot...

You guys are getting me to think about this more and more, with every post. Keeping in mind what you have stated nikon, and realizing that we probably wouldn't use a 65 lumen light "close-up" anyway, would you say that the farther away the target we are shining the light on happens to be, the less visible the "null" area will be? How about you Don, am I thinking logically?

Re: L4\'s 5 watt Luxeon dark spot...

The donut effect certainly becomes less obvious and less relevant at greater distances as the total output of the hotspot blends together. In normal use of the light I'm unaware of the donut.

Re: L4\'s 5 watt Luxeon dark spot...

I feel much better now, not having tested the bezel at great distances. Thank you. I am so glad that I have an L1 for close-up illumination needs! Regardless, SureFire lights are something else....

Re: L4\'s 5 watt Luxeon dark spot...

If I am correct, or even close, the "X" you see up close is because the light has still to converge and cross paths as it does further out. This "X" or hole is also there with a single die Luxeon and even an incandescent. I believe what you are seeing is the shadow of the LED or incan lamp itself and it has nothing to do with the cross seperating the dies in the 5W.

As far as tint and output go, I don't think there is any correlation of tint to output across the population of the Luxeons. I suggest that on any particular LED, removal or thinning of the phosphor would probably allow more of the blue photons out and likely the LED's flux would increase as its tint becomes more blue. I have a pet theory that the over achievers in photon generation put out more photons than the "standard" phosphor coating is designed to process and as a result you get some artifacts of blue where the phosphor is too thin and yellow where the phosphor is thicker. I think the *real* bad boys here tend to be the ugly ones! /ubbthreads/images/graemlins/nana.gif that's my pet theory and I don't want to be confuesed by any facts, thank you very much!

Re: L4\'s 5 watt Luxeon dark spot...

What McGizmo says about size and moving back the emitter is true.
An example of 99% null elimination is found on my 5W Nuwai. It's head is larger in dia than the L4 a friend of mine has. It also is focusable to a significant extent for extreme closeup use, or longer projection.
It ain't a Surefire but they sure did a nice job for what this Nuwai costs.
-And the very best white (on this particuler light, anyway) that I've ever seen. /ubbthreads/images/graemlins/thumbsup.gif

Re: L4\'s 5 watt Luxeon dark spot...

Don,

I am so glad that I posted this message. I have learned more from you about the Luxeon emitter in one sitting than in all of my days since my 4/17/04 registration with CPF. Now, I am even more obsessed with learning about how Lumileds gives us these wonderful Luxeon emitters, and I will read as much as I can about them ASAP.

I must dispute your comment about the single die image being visible. My L1 bezel with a 3 watt Luxeon has no visible "null" area, regardless of how closely I place the light to a white surface. If it is there, it has to be after my ability to detect "any" light occurs, which is after the scalloped lens housing is resting on the white surface.

Re: L4\'s 5 watt Luxeon dark spot...

Luxlover,

Sorry, I was referring to reflectors and not optics. I presumed this discussion was about reflectors. If your L1 had a reflector instead......... /ubbthreads/images/graemlins/tongue.gif

Re: L4\'s 5 watt Luxeon dark spot...

Ah hah! If my L1 with a 3 watt Luxeon had a reflector instead of an optic, then I would also see the "null" just like my L4 with a 5 watt Luxeon. An optic projects the square die but hides the "null", and a reflector hides the square die but projects the "null." I am learning that there are pros and cons in both beam projecting devices. I must decide which qualities of the light pattern are appealing to me. I am sure that the less that I see, other than the beam itself, the better it will be. As long as I use the L4 to illuminate targets farther away, and the L1 to illuminate targets a little closer, I will probably not notice the defects in the beam pattern of each light. Good lesson, Don.

Re: L4\'s 5 watt Luxeon dark spot...

Luxlover,

Many of the 5W's in reflectors will have some hint of a null. I would expect it fair to call these artifacts. Many lights have artifacts which detract little when you are concentrating on the message and not the messenger. There are artifacts or uneven fields of illumination levels within most ambient lit situations; artificial or from the sun. How often is one aware of these artifacts unless they are blatant like sunlight through louvered blinds or other heavy cast shaddow or areas of strong reflected light? You go into a room and hit the light switch and look around. The lighting may suck but but you can see what uyou need to see and don't give it a moments thought. If however, you have just installed new light fixtures, you will be acutely aware of the photonic landscape.

Don't get me wrong, the null from a 5W can be very anoying as one intuitively expects the center of a beam to be as bright if not brighter than the surrounds. Even with this noticible flaw, I suspect that typically if one were to use such a light in a needed illumination activity that the null could get by unnoticed. Without looking, how clean are your windows? How clean are your glasses if you wear glasses? The message can come through loud and effectively clear even if the messenger is butt ugly! /ubbthreads/images/graemlins/tongue.gif

Re: L4\'s 5 watt Luxeon dark spot...

Right on Don! Two of my three KL4's exhibit the "dreaded" donut, and it actually did bug me for a while. But then I tried to think of situations where the slight black hole would be a problem or even a minor detriment, and I couldn't think of any. After that it didn't bother me at all.

John

Re: L4\'s 5 watt Luxeon dark spot...

Good point, Grasshopper!!!! I agree with you in that I should enjoy the light and not obsess over any flaws that do not detract from it's purpose. Don, when I grow up I want to be "just like you!"

PS: My eyeglasses lost their anti-scratch coating a while ago, and are pretty well beat up. I am too cheap to lay out another $250 for a new pair right now. Bottom line is that I can see with them as is, and unless I take them off for close inspection, I am not bothered by some of the "null" areas of the lenses.

Re: L4\'s 5 watt Luxeon dark spot...

I want to be just like you too, kubolaw. I am realizing that I must ease up some of my strict requirements for lights, and enjoy the ride more. I very much enjoy my L4, and the more I study SureFire's products, the more I want them. Since we are already on the topic of the L4 light, may I recommend to all of you a post that I submitted yesterday, concerning the KL4/E1e combo? It can be found here.... "KL4 bezel + E1e body........Makes sense?"

Re: L4\'s 5 watt Luxeon dark spot...

Hi guys,

My posts here rely heavily on my sig line and I was really hoping some of the members who actually know what is going on with these photon canons would chime in. /ubbthreads/images/graemlins/frown.gif For a data point, I just finished up a mod last night that uses a 5W in a 33 mm reflector. I know where the focal point of the reflector is since I designed the dang thing. With a Lux III in this reflector, you get a great beam with the die positioned where one would expect. Initially with the 5W, I had it positioned "in focus". Looking into the reflector, all you saw was nice gold from the phosphor. Lighting it up guess what I got! Yup, Mr. nasty in the center of the beam. I shimmed the reflector up .015" from the LED and the null was gone.

Philosophical export: In reality, some things in life look better if viewed slightly out of focus. /ubbthreads/images/graemlins/nana.gif

Luxlover, I suggest that you aim *much* higher in your plans for growing up. I for one, have no intentions of ever growing up; stuck with the growing old part though. /ubbthreads/images/graemlins/banghead.gif