What is the deal with the "doughnut hole"???

[painless]

Is this something that has to do with the whole "sometimes you get lucky and sometimes you don't'' deal that I hear about with LEDs? Or is it a charicteristic of certian LEDs ? Does it happen with most LEDs, but only evident using a smooth reflector?

Or do you have to spend over $120 to eliminate this phenomenon?

 

[Nitroz]

It is usually caused by either a bad focal position for the LED, or the incorrect reflector being used for the particular LED.

For instance, a Cree LED does not work well in a stock Mag reflector, whereas the Seoul P4 is a much better option.

No you do not have to spend $120 dollars to fix it.

 

[mskerritt7]

Good question. I'm also interested in hearing the response. It's the most important factor, for me, in choosing a light, and is currently the reason i love my TK10 but am less than thrilled with my P3D- and they use the same emitter. :shrug:

 

[knightrider]

Doughnut holes are delicious! I like the plain ones the best! My L2 has one but my L4 doesn't. Mmmm.... doughnut holes!

 

[painless]

Thanks for the reply. It is my MA6 with the Q5 WC.
With the OP installed, it is eliminated by softening the beam patern.
But I got this light for its throw potential in a smaller size, therefore the smooth is used more. It is evident in across the room and down the hall use, not at 50-100yds. It is more of an annoying issue than anything I guess. I just wish it wasn't there. I have been called picky before. Oh well.

 

[Yoda4561]

Even with reflectored lights it's a bit of a lottery. Usually though with a decent reflector/led match most will not have any sort of donut hole, but if one or the other is just a hair off it will throw the focus and you'll get rings/donut holes to varying degrees.

 

[Hitthespot]

It can be a result of the led being set too deep or too shallow in the reflector (sometimes). I once had a Olight T20-Q5 that had a slight hole in the middle of the spot. After about two weeks I accidently dropped the light on the floor. It hit tail down. After that the hole was almost non-visible. I fixed it by accident.

As someone else mentioned, I think the Cree Q5 seems to be much more likely to have holes than other LED types. Holes and especially rings seem to be a Cree trademark. I'm sure there are others here who can explain why much better than I can.

Bill

 

[Flashlight Aficionado]

Again, no expert here.

To avoid confusion on my post. LEDs have a light source (that actual Light Emitting Diode) and a glass/plastic/etc clear/colored lens. Best that I understand it, anyway.

I thought the donut holes occurred primarily from multiple light sources(LEDs) under a single lens. Where the are (usually four) LEDs under a single lens. Such as in the infamous U2. Where the four LEDs meet, is where the "hole" appears. When there is only one light source under the glass, there is no empty spot to cause a hole. I am sure cheap lenses could also cause holes on single LEDs.

Well that is how I understood it. If I am wrong, call me an idiot and tell me the real answer.

 

[Marduke]

Donut holes are just an artifact of the focal charistics of the reflector/optic being used. If you think it's for LED's only, pick up a stock incan MagLite some time. :sick2:

It has the worse of all. Sometimes they are also only visible within the first few inches of the beam, after which the beam comes into focus.

 

[Flashlight Aficionado]

Marduke - The OP was only talking about LEDs. Oh, I know practically nothing about incans, so I am not arguing with you.

 

[enLIGHTenment]

As someone else mentioned, I think the Cree Q5 seems to be much more likely to have holes than other LED types. Holes and especially rings seem to be a Cree trademark.

Bad beam quality isn't a problem caused by the XR-E. Rather, it's a problem caused by flashlight manufacturers using reflectors not designed to work with the XR-E. It's quite possible to produce a good beam with the XR-E; it just takes a properly designed reflector (see i.e. the LF5XT) or, better yet, a TIR optic (see i.e. SF's Cree-based lights). When you see a Cree light with a bad beam, blame the light manufacturer for using the wrong optical parts.

 

[Hitthespot]

Bad beam quality isn't a problem caused by the XR-E. Rather, it's a problem caused by flashlight manufacturers using reflectors not designed to work with the XR-E. It's quite possible to produce a good beam with the XR-E; it just takes a properly designed reflector (see i.e. the LF5XT) or, better yet, a TIR optic (see i.e. SF's Cree-based lights). When you see a Cree light with a bad beam, blame the light manufacturer for using the wrong optical parts.

Your right and I said it badly. Good Clarification.

Bill

 

[Kiessling]

Usually, the donut hole is not a problem with single-die LEDs unless you have a really mismatched reflector/LED combo.

It is the LuxV that made that problem famous as it is a 4-die LED and quite difficult to focus properly. A lot of the LuxV lights do have a donut when properly focussed, such as the SF L4/5/6 et al.

bernie


P.S.: please note that any light will express a donut (more or less) when you shine it on a wall from a very short distance. That does not count though ... the beam just doesn't have the distance to collimate properly.