Fenix LD41 - doughnut hole?

boet

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Hi Folks, I have recently tried out four different Fenix LD41's. When shone on a wall, each exhibited a dark / blotchy center circle, with the outer circle of light brighter/whiter. Is this to be expected from this particular flashlight given its LED type? The beam is not pleasant to look at indoors- and I realize it will look different outside. Thanks for any answers. By the way, I cannot seem to move my cursor around to format / paragraph my post. Thanks for any answers. Cheers. Boet.

Added to clarify:
By doughnut hole I mean that the large hotspot is not as well lit as and is noticeably darker than the corona and about the same as the side spill. (Ha, I looked up the descriptions, which I should have done before).
I don't mean a black unlit hole in the centre.
Hope that is explained better. Apologies if my initial description was not clear.
 
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Labrador72

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Re: Fenix LD 41 - doughnut hole?

I think is very common for lights with a smooth reflectors and first generation XP-G and XM-L LEDs. Most of my lights with these emitters do have a doughnut hole though a few don't.
I have 3 lights with an XP-G2 R5 and none of them has even a slight doughnut hole.
 

Norm

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Re: Fenix LD 41 - doughnut hole?

Some reading for you.

Shame on you White Wall Hunters!!!

Just curious why there is a term being used in a derogatory manner as of late.

The phrase "White Wall Hunter" has been coined and popularized to refer to people who enjoy shining their flashlights on the walls of their humble abodes . The inference of this phrase seems to be ;

" I am a flashlight professional and would never, ever give in to the temptation to shine my flashlights onto a wall and thus make a judgment on the quality of its beam in any way. Since the act of shining a flashlight on a wall is completely pointless and has no bearing on real world applications of any given flashlight, which is a tool first and foremost, and not a toy to be used for ones amusement ... I am deeming those who do as such to be of an inferior class of people who cannot possibly posess a valid opinion . These "white wall hunters" obviously do not understand the seriousness of their actions . The wasting of all those valuable photons is shameful and so indicative of a novice flashlight user it borders on criminal and as such I shall bestow upon them the "scarlet letter" term of "WHITE WALL HUNTER" !! "


Well, unfortunatley I must confess as others should also so as to redeem your soul I AM A WHITEWALL HUNTER!!!!!!!!!!! I have been know to wander around my house firing photons at walls like a postal worker on crack cocaine holding an UZI . and i will tell you a secret of which even I am ashamed of. As of late, when I go into the bathroom to do my business, instead of reading a magazine I find myself bringing a flashlight in with me , shutting the door , sitting down and turning the overhead lights off and playing with the flashlight. My girlfriend is completely unaware of this though I think she suspects something is going on because I have forgotten the flashlight on the sink a couple times and used the excuse I was looking down the drain for a clog. I dont think she belives it .

But, does this mean I don't use my flashlights in real world applications? what are real world applications? Well I had to use a flashlight on my motorcycle once. The bulb blew on my headlight so I used electrical tape to lash my trusty flashlight to my handlebars and thus made it home on completely unlit backroads safely.

I have used my flashlight to keep my 7 yearold son from plummetting down unlit concrete stairs. I have used my flashlight to search for an errant nail in a car tire . I have used my flashlight to check the level of antifreeze in my cars overflow tank .
Yet I shine my lights on walls and marvel at their beams while I watch T.V.

What I would like to know is, what real world applications do NON-WHITE WALL HUNTERS use their flashlights for that I am not. :)

white wall hunting site:www.candlepowerforums.com

Norm
 

CarpentryHero

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Re: Fenix LD 41 - doughnut hole?

I like having the beam profile I want, whitewall or not LoL

as stated above the original smooth reflectors with gen1 Cree xpg had the donut hole beam, I didn't see it much in XML and I'm a little surprised its in the LD41. I have the Jetbeam pa40 and its almost identical in size and performance (Fenix is brighter)

i didn't like the LD10 LD20 or PD30 with the R5 xpg due to the smooth reflector and donut hole beam. I tracked down OP reflectored Q5 because the xpg2 wasn't out yet
 

Verndog

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Re: Fenix LD 41 - doughnut hole?

I dont spend much time on white walls other then occasionally comparing one tint to another...that said, I've never noticed any doughnut on my LD41 U2. My LD41 I use strictly outdoors, and find the beam profile and tint very acceptable. Not my best 4A but good IMO.
 

boet

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I like having the beam profile I want, whitewall or not LoL

as stated above the original smooth reflectors with gen1 Cree xpg had the donut hole beam, I didn't see it much in XML and I'm a little surprised its in the LD41. I have the Jetbeam pa40 and its almost identical in size and performance (Fenix is brighter)

i didn't like the LD10 LD20 or PD30 with the R5 xpg due to the smooth reflector and donut hole beam. I tracked down OP reflectored Q5 because the xpg2 wasn't out yet

Larf.
OK, I admit I've been naughty shining my lights on The Wall.


I use my lights a lot indoors and cannot resist the temptation and reserve the right to flash any and all walls that take my fancy. The downside is that I cannot tolerate a doughnut hole staring back at me like a one eyed ogre.

As CarpentryHero alludes to above, I want a good beam profile and
colour that does not bother me when using the light. I have many other lights that do not exhibit the doughnut and have a nice smooth beam with good colour.

To rephrase my query:
Is the Cree XM-L U LED as found in the Fenix LD41 prone to producing a doughnut?
Is that just the way this LED is, and I must therefore move on to something else?
Maybe it's the smooth reflector in the LD41 that is causing the doughnut?

Woe is me as I really like the form factor of the LD41.

Thanks for any insight.
Cheers.
 
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Verndog

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Just checked my light again, and absolutely NO doughnut hole. Version U2 bought about 6 months ago.
 

Labrador72

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To rephrase my query:
Is the Cree XM-L U LED as found in the Fenix LD41 prone to producing a doughnut?
Is that just the way this LED is, and I must therefore move on to something else?
Maybe it's the smooth reflector in the LD41 that is causing the doughnut?
Smooth reflectors + XP-G or XM-L are likely to produce a doughnut hole. To give you an example, out of 3 Fenix PD31 with XP-G R5, two have a doughnut hole, one not even a slight hint. It's kind of a lottery and usually not one with good odds. Even with an OP reflector you could still get it, probably less marked and less visible but I do have at least one XM-L light with OP reflector with a doughnut hole too.

It doesn't really bother me as outside it's not noticeable, at least not on my samples. Inside is not that bad either provided the beams don't have other highly visible artifacts.

I wouldn't bother unless it's too bad. I totally understand you though: hate peripheral rings, when I get lights with peripheral rings I get depressed!
 

boet

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Thank you for the above replies.

To clarify:
By doughnut hole I mean that the large hotspot is not as well lit as and is noticeably darker than the corona and is about the same as the side spill. (Ha, I looked up the descriptions, which I should have done before).
I don't mean a black unlit hole in the centre.
Hope that is explained better. Apologies if my initial description was confusing.

Thanks again!
Boet
 
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inetdog

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Thank you for the above replies.

To clarify:
By doughnut hole I mean that the large hotspot is not as well lit and is noticeably darker than the corona and side spill. (Ha, I looked up the descriptions, which I should have done before).
I don't mean a black unlit hole in the centre.
Hope that is explained better. Apologies if my initial description was confusing.

Thanks again!
Boet

What you are describing also is very similar to the lens characteristic that photo buffs call "boke" (pronounced bouquet :)). It refers to the shape of the image of a point source of light which is out of focus. When the lens (or reflector) defocus goes in one direction (out of focus foreground) you get a different result than in the other direction (out of focus background). Neutral boke is a uniform light over the blur circle (ideal to the lab guys, but not the most desirable in photos with deliberately limited depth of field). Good boke is a blurred circle, brighter in the center, and bad boke is a donut hole.

The problem in the case of an LED flashlight is complicated by the fact that the LED is not actually a point source, but I think you can also associate this with the effect seen in incan mag lights where defocusing in one direction produced a blurred hot spot and in the other direction produced a mild donut hole.

The donut hole on the wall may in part be the effect of the compromise focal position of the emitter for nearby targets.
 

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