SF U2 - What to take note of?

[Hoya]

Hi flashaholics,

I am getting the U2 but before that I would like to have some good answers/feedback to the following qns.

1) Tint issue - Is there an U2 that has CONSTANT TINT for all the light levels. I don't really mind slight greenish tint but I really cannot stand multiple tint in one flashlight. It had better all greenish or all bluish or whatever, I just dun want green in lower beam, white in middle beam blue in high beam in one light, that is really awful and distracting. After my expereince with my L2, I will be careful about buying multiple stage lights. I have seen smoeone's L2 with bright blueish low level beam, I am wondering is his L2 defective or mine (with greenish low beam). Are there any resources that I cna get to read about Lux V behaviour on low voltage. Should it be greenish when they are driven at lower voltage?

2) Is there a natural HA3 version of the U2? How do you tell if the HA in U2 is level 3? Well, I thought HA3 anodizing is only OD. Is there such thing as a black HA3? This maybe a stupid qns. But I am still learning...

3) What other things to look out for? Switch? Selector? any known issues? Need advise.

I am just another newbie. Thks in advance.

 

[NewBie]

The main color, green, white, blue, pinkish, purplish, etc., varies from unit to unit.

Proper focus of the LED in the reflector, some units have a big donut in the beam.

Centering of the LED in the reflector, creates wierd comet looking effects in the beam, a.k.a. coma.

Thats just from units I've seen at the local Sportsman's Warehouse store.

 

[Hoya]

Thanks Newbie! (Umm...newbie??? /ubbthreads/images/graemlins/smile.gif) Well, I am ok with slight tint of any colour, be it green,blue, pink...etc. But I m more concern about the homogeneousness of the tint for level 1-6. Have you seen an U2 with an uniform tint thoughout 1-6? I am not being picky, but at $270.00 a pcs, I expect SF to pick a good LED for the U2 which is also their Ultimate LED?

[ QUOTE ]
NewBie said:
The main color, green, white, blue, pinkish, purplish, etc., varies from unit to unit.

Proper focus of the LED in the reflector, some units have a big donut in the beam.

Centering of the LED in the reflector, creates wierd comet looking effects in the beam, a.k.a. coma.

Thats just from units I've seen at the local Sportsman's Warehouse store.

[/ QUOTE ]

 

[ho71ko]

1. Sorry, I can not comment in a qualified manner on this topic. There are others here on the Board who will chime in here and have proper knowledge.

2. I can confirm that it is Black HA III. There have been previous series of Black HA III Lights by SureFire like the black E2e. These things have become collectors items because there haven't been much hitting the streets.

3. No issues on the U2 I have heard/read about. The U2 is a clever light that is as well build as one would expect from SureFire.

Holger

 

[KevinL]

The U2 is only available in HA-black. There was never a Type II version released to the public, so you're getting HA.

Mine maintains the same tint as I step through all six levels, but I only have a sample size of one unit, so it may not necessarily be representative.

LumiLEDs themselves warn that Luxeons may be 'subject to variations in performance' (probably color too) when driven at lower currents, which the U2 does - it uses constant-current regulation. LumiLEDs recommends PWM for dimming. (DS40, Luxeon V Portable datasheet) For example, Mr Bulk's Lionheart/Lioncub are dimmed by PWM and thus would not experience color shifts.

 

[turbodog]

The U2 is a nice light, no doubt. I had one of the first ones. I also just sold it.

It runs well on a pila 168s/168a cell.

Tint is pretty much the same at all levels. No major shifting.

Donut? It's there with most all surefire lux v lights.

The light can be gotten for about $230 at www.ultimatepassage.com

I would not buy another. The HDS light does 90% of what the U2 does, and some things it doesn't. I absolutely hated the U2 clip. I use a light on my hat a lot and the clip faced the wrong way.

 

[Hoya]

Hi turbodog , so you are sold to the HDS. How much did you pay for it and lead time? I am kind of interested in the Ultimate 60 too.


[ QUOTE ]
turbodog said:
The U2 is a nice light, no doubt. I had one of the first ones. I also just sold it.

It runs well on a pila 168s/168a cell.

Tint is pretty much the same at all levels. No major shifting.

Donut? It's there with most all surefire lux v lights.

The light can be gotten for about $230 at www.ultimatepassage.com

I would not buy another. The HDS light does 90% of what the U2 does, and some things it doesn't. I absolutely hated the U2 clip. I use a light on my hat a lot and the clip faced the wrong way.

[/ QUOTE ]

 

[Hoya]

ok. Seems like I have to drop by the camping store to test the U2 personally. It would be 'risky' to buy online as I may receive a multi-tint U2.

 

[wasBlinded]

Definitely best to try the sample you want before you buy. I got a very green one, which I hated. Surefire made good on it, however, and now I have one that is snow white at all levels.

I really like the light, but there is a lot of unit to unit variation that you will not see with a LuxIII based light - at least not to the same extent.

 

[cliff]

Hoya:

My U2 is white at all levels and the slight donut it has is not an issue. The LED on mine fizzled out after the first 30 days and the tail cap sometimes had to be clicked a few times before turning it off. It was in the SF shop for two months but they fixed everything. The new tailcap has no flaws and the LED is as white as the first.

There seems to be mixed feelings about the clip. Personally it works out well for me and bezel-down in the back pocket is not a problem. For hands-free use I made a "lanyard" of a 16" long cord with Berkely Point mini-clips whip-spliced at both ends. On one end I clip to a "No-mar" clothespin with a 1/4" hole drilled in one of the tabs. The other end is clipped to the light's pocket clip. The clothespin is then attached to a shirt pocket or lapel and the line is draped over the back of the neck. This holds the light on the shoulder pointing at whatever I'm doing and you don't end up on a gallows if your light goes one way and you go the other. If the light had a bezel-up clip, this arrangement would not work.

 

[Luna]

[ QUOTE ]
tail cap sometimes had to be clicked a few times before turning it off.

[/ QUOTE ]

I guess it was last week when you gave me SF tech support number and i got the new switch tuesday. Not a bad deal plus I fixed the old one with the technique posted here and put the clickie on a very old 6Z rig ->now 6P+a19+Shock isolated bezel setup. Considering the price of the U2 ($225) and the spare clickie that I was planning on getting anyhow, the u2 basically cost me the same as a L6 /ubbthreads/images/graemlins/smile.gif

The new switch is tighter too, which I like

 

[chamenos]

tint shift is currently endemic in all white LEDs, probably due to a non-linear variation in the reactivity of the phospher coating, relative to the output of the blue LED underneath, and there's no getting around that. PWM lessens this effect, but it won't completely solve the problem. the fault lies with the current technology available, and not with surefire /ubbthreads/images/graemlins/smile.gif

 

[NewBie]

[ QUOTE ]
KevinL said:
LumiLEDs themselves warn that Luxeons may be 'subject to variations in performance' (probably color too) when driven at lower currents, which the U2 does - it uses constant-current regulation. LumiLEDs recommends PWM for dimming. (DS40, Luxeon V Portable datasheet) For example, Mr Bulk's Lionheart/Lioncub are dimmed by PWM and thus would not experience color shifts.

[/ QUOTE ]

Actually, the color does shift even with PWM. It just shifts less then current dimming.

Here is actual measured data:

The other bad thing about PWM dimming is the emitter's efficiency actually drops when dimmed, when compared to a current dimmed light:

 

[KevinL]

Ahh, I see, LumiLEDs didn't mention that. No wonder Surefire went with a constant-current design for their U2, since it does away with the efficiency hit. Thanks for the graphs!

 

[NewBie]

Here is what happens at 1140mA of drive, much like the LionHeart:

Notice how there is not nearly as much of a difference in the colorshift at the higher drive current, when comparing constant current vs. PWM.

And you pick up alot more efficiency when dimmed:

 

[Ray_of_Light]

I fully concur with you, Newbie...
the PWM dimming technique was invented for motors and incandescent bulbs, or device with their own "inertia"; mechanical inertia in the case of motors, thermal inertia in the case of filament bulbs.
In the case of LEDs, the PWM dimming keeps the peak current always at maximum, relying on the integrating power of the human eye to perceive the lower brightness. The LED is ALWAYS at max power, whenever it is ON.
Since the efficiency of the LED is a proportional (among other things) to the number of majority carriers that are NOT recombining, a PWM dimmed LED cannot show any efficiency increase in terms of lm/W, as in the case of current dimming. There is only a thermal advantage, due to the total dissipated power being of lesser intensity.

Anthony

 

[cliff]

Luna:

If you could direct me to that technique you used for fixing your tailcap it would be much appreciated. My new tailcap is now malfunctioning, but instead of not clicking off it won't click on.

In addition to being a little irritated, I'm getting mighty curious as to what is wrong with these specific tailcaps.

 

[Luna]

[ QUOTE ]
fully concur with you, Newbie...
the PWM dimming technique was invented for motors and incandescent bulbs, or device with their own "inertia"; mechanical inertia in the case of motors, thermal inertia in the case of filament bulbs.


[/ QUOTE ]

Though I agree that current is the way to go if die life and efficiency are the intent, you cannot neglect the fact that the phosphors have an "inertial" nature to them much like the tungsten filament.

 

[LitFuse]

cliff (or anyone else)- if you can't fix your TC, I'd be happy to do it for you. All I ask is for $1 to cover a bubble mailer and return postage.

Peter

 

[chrisse242]

[ QUOTE ]
NewBie said:
Here is what happens at 1140mA of drive, much like the LionHeart:

Notice how there is not nearly as much of a difference in the colorshift at the higher drive current, when comparing constant current vs. PWM.

[/ QUOTE ]
Newbie, I'm not sure I understand this graph, maybe you can help me. What do the numbers on the x and y-axis mean? I thought the colour shift improvements of pwm come into play when comparing a high current/low duty cycle setup to a "low" current setup done via constant current regulation. Now, since you only mention 1140mA for this graph, you seem to be comparing the two systems at high constant current and high current/high duty cycle settings, where from my understanding the tint shifting should be negligible.

Cheers, Chrisse

EDIT: Second question, at what duty cycle-levels do pwm systems typically start?
For example, where on the second graph would the lion-hearts lowest setting be?