Lux measurement of U2 - UPDATED w/ MEASUREMENTS!! (Again!)

**Update 2: I posted two more runtime charts at post #37 on page two - check it out!***

**Update: I posted a new post at the bottom of the thread with my findings... Let me know what you think!!!***

Anyone know what an average Lux measurement at 1 meter (beam center), the Surefire U2 should be at brightest level?

Mine seems quite a bit dimmer than it seems like it should be, and I was going to take a measurement (which requires me to buy a meter), and wanted to have some numbers to compare it to.

flashlightreviews.com has it listed as 1885 lux, Cones-stuff has it at 1722. So that's something to base it from... anyone else's measurements would be appreciated!

On a related note, what is an acceptable amount of deviation? (Obviously taking into account that meters fluctuate in their readings)

Thanks guys!
john

Re: Lux measurement of U2

Problem here is the different beamshapes, and especially the donut hole, which means that you can get lower lux readings but still have a high flux and vice versa.

Because you asked, my U2s are the following:

#1 (very old) ~1750 lux
#2 (very new) ~1920 lux
#3 (exceptional performer) ~2460 lux

bernie

Re: Lux measurement of U2

Hello jch

I remember in this thread was a Lux reading of a U2 somewhere:

https://www.candlepowerforums.com/threads/112351

Best regards

____
Tom

Re: Lux measurement of U2

Thanks Bernie & Tom... I figured one of you would respond to this one :goodjob:

My old U2 was blinding, but had a huge donut hole and a broken clickie.

My new U2 has NO donut hole, a working clickie, but is noticeably dimmer, especially after it's been on for 5 seconds or so - such that you can look directly into the LED after it's been on for ~5 seconds without it hurting your eyes...

The light also gets much warmer than my last one, which I don't mind, but I can't help but wonder if the two symptoms are related.

I suppose I'll pick up a light meter (a local store has a Velleman brand) and test it and see what I come up with in intervals of 5 seconds.

Thanks guys - anyone else's opinions would be awesome!

Re: Lux measurement of U2

jch79 said:

My new U2 has NO donut hole, a working clickie, but is noticeably dimmer, especially after it's been on for 5 seconds or so - such that you can look directly into the LED after it's been on for ~5 seconds without it hurting your eyes...

Click to expand...

That doesn't sound good to me. You shouldn't be able to look down the business end of a U2 when it's on full bright with good cells. You'd be seeing spots for days.

I had a U2 that was about 1410 lux running an 18650 cell. It was 1760 on primaries. It had other problems and went back for RMA. The replacement light was about 2160 lux on li-ion. That was good enough for me, and I never really bothered to measure it on primary cells.

Re: Lux measurement of U2

Hello John,

With my U2, I am getting around 2178 lux with an 18650 and it jumps up to about 2328 lux when I use CR123 cells.

Tom

Re: Lux measurement of U2

Mine peaks at 1810 lux @ 1 meter, this is with CR123s that have about 10 minutes on them.

BTW, that is the beam brightness at peak, mine does appear to have a bit of a donut hole according to the meter (Sper Scientific 840006), but it is not readily visible to the naked eye.

Re: Lux measurement of U2

Ok~
Well, it looks like I should for sure pick up a light meter and measure this thing... and prepare to not be impressed!

Re: Lux measurement of U2

just curious, but the u2 cant run on protected 3.7v rechargeables can it?

-David

Re: Lux measurement of U2

It runs almost perfectly on a 18650 cell (brightes level mit be a tad dimmer though), the only problem is that the 18650 won't fit in the newer U2 bodies due to a plastic insert.
bernie

Re: Lux measurement of U2

After the emitter change, my u2 measures almost as high as the gladius. I forget the measurement offhand but it was over 3000lux best I recall I will retest tonight. Before the swap, it was a good performer at the 2200lux level.

Also, It ***seems*** that the S Vf has less of a difference when running primaries vs 18650s than before but that is from memory. I didn't chart the current at the emitter before the swap to be certain.

PS, running with 2 RCR123a it posted around 4000lux but that is about double the rated current of the LuxV.

Re: Lux measurement of U2

Ty_Bower said:

...light was about 2160 lux on li-ion. That was good enough for me, and I never really bothered to measure it on primary cells.

Click to expand...

I bothered to measure it on primaries tonight. I happened to have the light meter out, and a pair of lightly used Battery Station cells. It was between 2400~2600 lux, depending on how carefully it was aimed at the meter.

Re: Lux measurement of U2

so r123s would work in the u2, but the led life and battery life would be significantly reduced??

-David

Re: Lux measurement of U2

Since the U2 is likely boost-only electronic-wise I certainly wouldn't use 2 x Li-Ion cells !!!

Re: Lux measurement of U2

You lose the ability to select 6 levels of light with two 3.7v batteries so obviously it isn't designed for it.

Re: Lux measurement of U2

Ok!!

After a lot of searching, I FINALLY got a light meter (a Velleman brand - $50, and got the job done), and did my U2 test last night.

With fresh batteries, I took 1 meter beam center measurements every minute, for 70 minutes. I did not have the light in water or anything to cool it - it was sitting on a book.

The light measured 1924 Lux initially, and dropped about 100 lux within a minute, and gradually dropped 200 lux within the next 15 minutes.

Then light output dropped dramatically at 18 minutes, and slowly dropped after that.

Any opinions? Should this be acceptable? I hadn't expected that it would drop so much, so quickly.



Thanks,
john

Re: Lux measurement of U2 - UPDATED w/ MEASUREMENTS!!

Hello jch79

This result is alarming.

Can you repeat the test with help of a cooling vent?

This would be very interesting.

Good luck and best regards

_____
Tom

Re: Lux measurement of U2 - UPDATED w/ MEASUREMENTS!!

What is the best way to keep it vented??
Thanks!
john

Re: Lux measurement of U2 - UPDATED w/ MEASUREMENTS!!

What cells did you use?
bernie

Re: Lux measurement of U2 - UPDATED w/ MEASUREMENTS!!

Hello jch79

I have build a 12V PC-ventilator with a 220V Adaptor for cooling my batterie charger during charging.

Such one or a big one for cooling rooms in summer in front of the light should be ok.

Perhaps a hairdryer on cold for about 20 minutes. This should be enough to see a difference. Perhaps bellows?

Best regards

____
Tom