U2 not as bright as L5

I just done a metered comparison test between the U2 and L5.
The U2 (at max level) is 1/2 stop less bright than the L5.
I thought the U2 if not the same should be brighter than the L5.
Anyone here can help / comment?

Well, according to Quickbeam (flashlightreviews.com), U2 has the slight edge on throw, L5 has the slight edge on sidespill. So your measurements don't seem too alarming, as the difference really isn't that much. :shrug:

Testing variations can always skew Lux tests... how many tests have you performed to find these results?

Unless there is a HUGE difference, I don't think there's anything out of the ordinary happening here... white wall hunting and comparing with other lights is never a great idea if you think you've got a bright, white light. Although, we all do it.

john

dont email SF. call them instead..
definitely my U2 is much brighter than L5

jch79 said:

Unless there is a HUGE difference, I don't think there's anything out of the ordinary happening here... white wall hunting and comparing with other lights is never a great idea if you think you've got a bright, white light. Although, we all do it.

john

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I agree, we should not compare LEDs against each other. It makes almost all our bright white lights appear greenish or bluish...yet I still do it too....

But back to the point, I think it might also be the Luxeon lottery, as some L5s and U2s has donuts of varying degrees that would affect the beam and brightness.

My U2 does not have the so called 'plastic sleeve' inside the battery chamber (or how does it look like)?
will this make it the older (1st) generation? if so might the newer plastic sleeve version be brighter?

My tests were done at equal distance (fixed on stand) in a pitch dark room , using same set of batteries. light meter readings with various other Sf lights and battery combinations confirms my visual. the U2 is indeed 1/2 stop less bright and smaller spill than L5.
i'll call SF on monday.

AFAIK These both use the same reflector so the beam should be close to identical.
Differences in output could be from the L5 doing better in the Luxeon lottery than your U2. You might just have a very bright L5...

If the U2 seems dim compared to other lights you might consider returning it to SF.

rollee - if you have more room on your body for CR123 cell then your U2 is the 1st gen. this so called 2nd gen has this black tube inside your U2 body. it will not fit 18650 but you can remove by using this method below.

https://www.candlepowerforums.com/posts/1690469&postcount=201


and lastly the newest one is a solid body. CR123 cell will only fit. no room for 18650 but you can use also 17650.

the luxeon V short lifespan is to be blame...

I suggest you do a bounce test off ceiling for each light and record the lightmeter readings. Do this in a relatively small room, say a bathroom at night, or with no windows in daytime. Use same positions for each flashlight with lightmeter about two feet or so distant from flashlight. This is a crude way to measure overall light output, but is effective when comparing different lights.

Bill

T4R06 said:

rollee - if you have more room on your body for CR123 cell then your U2 is the 1st gen.

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Is that making diffrence in heads too?
I'm going to buy U2 with gen 1 body. Is that any diffrence in performance, light amount etc between generations?
Mike

sp5it said:

Is that making diffrence in heads too?
I'm going to buy U2 with gen 1 body. Is that any diffrence in performance, light amount etc between generations?
Mike

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they are all the same i think, just the difference now is the body.

i love mine, even it has donut. the tint is beautiful white, very bright! thats what you call "luxeon lottery"

Tests Ive done is as varied and precise I can possibly control.
My U2 definitely lacks brightness and i don't even like its spill, the beam pattern is annoyingly narrow.
I have many surefires and have various LED lights, even a 3W (2AA) chinese make ($15 cost in china-gift from friend) nonamebrand throws better and brighter!

I just spent $$$ on the U2, L5 and E1L together, I am extremely disappointed. For a $200+ flashlight, the U2 is the worst money (in my experience) anyone can possibly spend.

On the other hand, I will buy any L5 without hesitation, it is out of this world bright with a gorgeous beam, it is also 80bucks less than the U2!

Since my experience with this 1st generation U2 is poor, I cannot conclude if the newer generation (plastic tube) will perform better, and i hope it does.
I can however suggest to stay away from the 1st generation ones like a bad rash.

With regard to brightness, you can't conclude anything about all U2s and L5s from one sample of each. Too bad your U2 is a little less bright than your L5. Maybe you just got lucky and have an overperforming L5. That doesn't mean your U2 is bad. One half stop means your U2 is 25% less bright than your L5. That is not much of a difference, and un-noticeable (apart from beam characteristics) unless side by side comparisons are made.

On the other hand, I once bought a U2 that was truly an abysmal performer compared to a couple of others I had. Its maximum output was about half that of my brightest one (a first generation also), so there can be a lot of variability. Replacing the LED with a WWOT fixed it.

New U2s are more likely to be brighter, is my guess. The brighter bins of LuxV seem to be more plentiful now, so your chances of getting a dim one are probably lower than when the light first came out. Still, its a chance thing.

You are only interested in lux measurements? Have you tested for overall output of each light, not just lux, but spill and center beam combined in one light meter reading, a la bounce?

Bill

if the U2 only costs $140 I have no complaints.
when spending upwards of $200 plus plus, my expectations are otherwise.

I paid $240 for it, if people here thinks its ok to accept this U2 for what it is bla bla bla, I will sell you exactly what i paid for it. Or how about you buy an U2 that is like mine ( for the price of $275 SF www) an underperformer, can you honestly say you are absolutely thrilled with your purchase?

My pain on this U2 lemon is unbearable.

my u2 was brighter than any led i had ever seen even when copared to the l5 even ask rookie.

rollee said:

if the U2 only costs $140 I have no complaints.
when spending upwards of $200 plus plus, my expectations are otherwise.

I paid $240 for it, if people here thinks its ok to accept this U2 for what it is bla bla bla, I will sell you exactly what i paid for it. Or how about you buy an U2 that is like mine ( for the price of $275 SF www) an underperformer, can you honestly say you are absolutely thrilled with your purchase?

My pain on this U2 lemon is unbearable.

Click to expand...

If you're that unhappy with it then call SF and get a warranty replacement. Part of what your getting when you pay almost $300 dollars for one of their lights is great customer service. If you feel you have an underperformer, they should swap it out for you with a different one. If the U2 just isn't for you (just because it costs $270, it doesn't mean everybody will like it) then sell it here on the BST board and get something that tickles your fancy.

I think that many people are quick to criticize SF's various issues (donuts, tailcaps, etc.) w/o truly appreciating the scope of their warranty service. The premium paid for a SF product entitles you to a light that works as promised. Once in a while that means a warranty claim, and at least we have that option.

Be careful For Luxeon V brighter means die faster.So it's ok if they can cover your need!

Bullzeyebill said:

I suggest you do a bounce test off ceiling for each light and record the lightmeter readings. Do this in a relatively small room, say a bathroom at night, or with no windows in daytime...

Click to expand...

Ditto that. A bounce test will tell you a lot about the overall output of each light.

Flashlightreviews test of the U2 and L5 shows the L5 has slightly more output, but the U2 has better throw. However that's a sample size of one.

There can be considerable unit-to-unit variation. Doing lux meter bounce tests as described above, my U2 outputs roughly 2x my HDS U60, which are supposedly individually calibrated to 60 lumens. My first U2 wasn't as bright, plus had tail switch problems, so there is variation. You can return it to Surefire for a replacement.

For a given light, there are (at least) two beam widths involved, the spillbeam beam angle and the hotspot beam angle. There is also a division of the light's overall output between spillbeam and hotspot. Some lights put more output in the hotspot and less in the spillbeam, and vice-versa.

Besides the actual output level, the division of output between hotspot and spillbeam, plus the beam angle of each all drive our visual perception of "brightness".

The U2 diverts a lot of output (about 79%) to its spillbeam, which is very bright. However the U2's spillbeam angle is relatively narrow at about 60 degrees. The U2 hotspot beam angle is about average at 8 degrees.

By comparison the HDS U60 diverts about 73% of output to its spillbeam, but has a spillbeam angle of 74 degrees.

The A2 (on incandescent) diverts only about 44% of output to its spillbeam, leaving more for the hotspot. The A2 incan. spillbeam is a broad 100 deg, so it's relatively dim. The U2 spillbeam by comparison is narrower and very bright.

Spillbeam measurements based on a single lux measurement at 1/2 the spillbeam radius, so it's a crude approximation but roughly illustrates the differences.

You tend to get accustomed to a given light's characteristics, then the next light compared may look odd. E.g, My U2 spillbeam angle normally seems fine. However when I use my A2 for a while which has an approx 100 degree spillbeam angle, then switch back to the U2, the U2 spillbeam seem very narrow.

I don't have an L5 to measure the spillbeam angle, but the hotspot beam is likely broader than the U2, based on FLR data. The U2 beam angle may seem narrow by comparison, but in actuality the U2 has a general-purpose hotspot beam width, roughly the same as the HDS U60 at 8 degrees. The U2 spillbeam angle is a little narrow.

The U2 is a great light; I'd suggest returning it to Surefire and asking for a replacement if you're unsatisfied in any way. The variable output has great utility, vs a single-level light that's often too bright and quickly depletes batteries.

If you want a completely different light that gives some of the U2's characteristics in a smaller package, try the A2.