XM-L Lumens?

eric_wolf · Dec 7, 2011

I have noticed that 4Sevens has XM-L lights (Maelstrom X7) which they rate at about 480 Lumens while I am seeing other vendors on-line listing XM-L lights at 1000 lumens. I am curious about the large delta in lumens.

Is the delta because they:

*aren't the same type of XM-L LED?
*are the same LED but being driven differently?
*are the same led but venders are overstating the lumens or counting lumens at the emitter vs Out The Front?

Finally, assuming these are the same LEDs and the brightness is the same, I am curious if people feel the chinese lights found on DealExtreme that are about 1/3 the price of the 4Sevens model are a case of "you get what you pay for".

alpg88 · Dec 7, 2011

eric_wolf said:
*are the same LED but being driven differently?
.

yes

peterharvey73 · Dec 7, 2011

At zero amps, the XM-L will produce zero lumens of light.
From zero to three amps, it will produce so many lumens of light; you must go to the Cree website, and look at the emitter's current/brightness graph.
At 3 amps, it will produce about 1000 lumens of light.
It can even be driven above 3 amps, to produce more than 1000 lumens of light, but this is not recommended by the manufacturer Cree...

LEDninja · Dec 8, 2011

*aren't the same type of XM-L LED?
Practically everyone uses the same T6 ANSI 1 tint XM-L.
*are the same LED but being driven differently?
CHECK
*are the same led but venders are overstating the lumens or counting lumens at the emitter vs Out The Front?
CHECK
Some vendors actually measure OTF lumens.
Some vendors calculate LED lumens from the drive current.
Some vendors use the biggest number they can find.
Some vendors play the one-up-man-ship game. Lets see now SSC-P7 is 900 lumens (does not matter SSC rate the P7 at 700-800 lumens). So an MC-E must be 1000 lumens! Or a SST-50 must be 1100 lumens!! So it follows an XM-L is 1200 lumens!!!

Finally, assuming these are the same LEDs and the brightness is the same, I am curious if people feel the chinese lights found on DealExtreme that are about 1/3 the price of the 4Sevens model are a case of "you get what you pay for".
http://www.candlepowerforums.com/vb...ght-I-have-bought-have-failed-except-a-couple.
"When I first heard about Dealextreame I was amazed that you could get flashlights so cheap compared to the Surefires and Maglights I was used to. I went a little crazy and bought a bunch of different brands and models over about a year. Long story short, most failed rapidly with very little use and zero abuse. I had a Trustfire Fail just sitting in the drawer for a few weeks."
You get what you pay for. Ditto eBay. Though this particular person is extremely unlucky.
I had one die within a week. One with a flaky UI. One in which half my batteries won't fit. From less than a dozen lights bought. I mostly try to buy only those that have no reported reliability problems.
And my Ultrafire 14500 batteries won't fit my Ultrafire 14500 charger! My AW 14500 do.

tre · Dec 8, 2011

eric_wolf said:
Is the delta because they:

*aren't the same type of XM-L LED?
*are the same LED but being driven differently?
*are the same led but venders are overstating the lumens or counting lumens at the emitter vs Out The Front?

Finally, assuming these are the same LEDs and the brightness is the same, I am curious if people feel the chinese lights found on DealExtreme that are about 1/3 the price of the 4Sevens model are a case of "you get what you pay for".

Yes,
Yes,
Yes,
Yes.

I know of one over driven custom built XML light that can do 1000 OTF lumens. I've never seen another. I guarantee any XML light you find that claims 1000 lumens is a complete fabrication - avoid that light because it is most likely cheap junk.

samgab · Dec 8, 2011

Here is some of Cree's info about the T6 and the U2 XM-L emitters, and the varying lumens output at a range of currents, from 1 to 3 Amperes:

So with a U2 rated XM-L run at 3A, you can get ~975.6 lumens out of it, at the emitter (when the junction temp is 25 degrees C).
I've seen tests showing that there is no benefit to driving them at higher than 3A.
As the temp at the junction increases, the lumens output decreases.
I don't see how one could get a genuine 1000 OTF lumens out of a single emitter XM-L light. You'd need to go to a multi-emitter setup.

jorn · Dec 8, 2011

LEDninja said:
Practically everyone uses the same T6 ANSI 1 tint XM-L.

Do they really? I wonder where all the T4, T5, etc are going. I think a lot of them "becomes a t6" as soon as they leave the cree factory and gets stuffed in a light. No one can check if it's the claimed bin anyway.

peterharvey73 · Dec 8, 2011

Just out of interest, in this thread @ Post 43
http://www.candlepowerforums.com/vb/showthread.php?326878-Cree-XM-L-vs.-Luminus-SST-90/page2

Saabluster says the XM-L U2 emitter can do 1040 lumens @ 3 amps 260 mm2...

samgab · Dec 8, 2011

peterharvey73 said:
Just out of interest, in this thread @ Post 43
http://www.candlepowerforums.com/vb/showthread.php?326878-Cree-XM-L-vs.-Luminus-SST-90/page2

Saabluster says the XM-L U2 emitter can do 1040 lumens @ 3 amps 260 mm2...

Hmm, well I don't know where that figure came from, but the chart posted above is the official data from Cree.
You can look it up at http://pct.cree.com and input your own product characterization parameters and see what you get.

LEDninja · Dec 9, 2011

You guys are starting to mix LED and OTF lumens.

The optics of a Maglite is ~65% efficient. (Plastic lens, powder coated reflector)
The optics of a Fenix is ~80% efficient. AR coated glass lens, polished reflector)

1000 LED lumens in a stock Maglite => 650 OTF lumens.
1000 LED lumens in a stock Fenix => 800 OTF lumens.

When Wayne Johnson of Elrktrolumens built me a Mag 3C P7 he shipped it with the stock Mag optics. I bought a replacement metal reflector and UCL lens right away.

yifu · Dec 9, 2011

Optics (TIR/aspheric) are >90% efficient compare to the 70 of reflectors. The XML is capable of ANYWHERE from 0 to 900+ lumens depending on drive current. To get more than 1000 lumens you'll have to overdrive it, 4-5A should do the trick, although the heat might be a problem.

LEDninja · Dec 9, 2011

yifu said:
Optics (TIR/aspheric]/b]) are >90% efficient

The aspheric is 90% efficient but you have to allow for losses due to light hitting the inside of the flashlight head behind the lens.

yifu said:

To get more than 1000 lumens you'll have to overdrive it, 4-5A should do the trick, although the heat might be a problem.

Click to expand...

For the 1st few seconds. At 4-5A the LED heats up more and the efficiency drops big time. There is a thread in the LED section where after a few minutes the XM-L driven at 3A is brighter than the overdriven ones.

eric_wolf · Dec 9, 2011

Thanks for all the great info!

tre · Dec 9, 2011

samgab said:
I don't see how one could get a genuine 1000 OTF lumens out of a single emitter XM-L light. You'd need to go to a multi-emitter setup.

Nope. It can be done and has. Kevin at Lambda lights drives the XML at 6A. He uses his direct copper to LED bonding method. I've measured my custom single XML from him at 1100 OTF lumens. Kevin tested another one at 1300 OTF lumens from a single XML. BigC also tested one of Kevin's single XML lights at 1100 OTF lumens. I use mine all the time and have no problem with too much heat. The batteries even last for about 1 hour on high. The whole body of the light gets a little warm but nothing like my over-driven SST-90 lights.

spc smith · Apr 8, 2012

So would using 16340 batteries with my Klarus be a problem. I know this is way off topic. And now I know alittle bit more about amps powering a single XML T6, U2 led emitter so thanks guys

XM-L Lumens?

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