SF U2 Beam Characterisitics?

Looking at the U2 review at flashlight reviews.com, there is a nice table comparing throw, overall output, and runtime on the various output levels. Some data points are included below with the Arc AAA as reference...

Level / Throw / Overall
1 / 43.42 / 55.00
2 / 32.86 / 32.50
3 / 25.10 / 17.82
4 / 18.03 / 9.42
5 / 12.84 / 4.83
6 / 8.25 / 2.25
Arc AAA / 7.28 / 5.20

The thing that jumps out is that the U2 appears to be very much a spot at lower outputs with the throw being "higher" by a factor of 3+. By the time you get to level 4, the factor is down to 2. By level 2, throw and overall output are equivalent. In comparison, the Arc AAA at output comparable to the U2 on low has throw and output numbers roughly equivalent.

I know these numbers are just for reference, but in use does the light act as indicated above: focused "spot-like" at lower levels moving towards more "flood-like" at higher levels?

Thanks,
Matt

You can see U2 beam in the thread passaround for Gladius. Gladius is compared to U2.

I currently have an U2. I had and sold an L4. I also had and sold an L6. To me:
- the L4 was mostly flood.
- the L6 was mostly trow, and not that good to me.
- I find that the U2 has a beam similar to the L6, but with more flood. So I found the U2 to be more practical/useful - that is why I sold the L6. Nothing wrong with the L6, but with the U2 I did not neded it any longer, the U2 is smaller, and I also gained adjustability /ubbthreads/images/graemlins/smile.gif

Will

So does that mean the U2 has the same relfector as the L5?

IsaacHayes,
Yes, I think so.
However, the U2 does come with a dome shaped lense which might probably help to focus the beam a bit more. I don't have an L5 to compare to, but it does appear almost similar to my L6 but my L6 definately throws significantly further.

I would agree with that statement. I felt the my old L6 had more trow than my U2.

When I said above that the L6 did not have good enough trow for me I was comparing it to my other 5W trow monster: I have a Surefire Turbo Head with a WX1T on an LED adapter running with a DB1000. Not as much trow with a 5W as when using a M*g reflector, but the M*G reflector is more of a pencil beam which I grew tired off. I guess is it all relative in the end /ubbthreads/images/graemlins/smile.gif

Will

From what I've .... Seen ......../ubbthreads/images/graemlins/cool.gif

........................ Heard ......../ubbthreads/images/graemlins/naughty.gif

and ................... Read ......./ubbthreads/images/graemlins/thinking.gif

The U2 has a well balanced beam !!!

Now that I have one, I have to agree. ..... /ubbthreads/images/graemlins/buttrock.gif

This flashlight stuff is intoxicating ....... /ubbthreads/images/graemlins/happy23.gif

txmatt, looking at the beam with the naked eye, the ratio of throw to flood does seem to remain constant. I don't see why it wouldn't as the reflector is not moving as levels are changed. Here are some pictures (sorry for my amateurish skills) to illustrate:

U2 beam on high (reduced exposure):



U2 beam on low (lengthed exposure to compensate for lower output):



As I hope is evident, the beam profiles are pretty much the same on high and low. The only difference I can see between the levels is a change in brightness overall.

Hope this helps,
-Brad

Brad, thanks for the shots. Yes, it does look like very consistent illumination between low and high.

I didn't know what to make of those numbers. I thought there might be something with differing drive levels of an LED causing different emmission patterns and thus a different balance of throw and flood as the drive current increases.

Darn, that's gonna make it harder to NOT buy a U2.

No problem. Quickbeam really does some great work, and the throw figures, since they are measued in Lux? are a very good basis to go by when considering how far a light will project its beam.

The overall output, since it is measured with a more makeshift (but ingenious) device is a little more open to error, so when looking at a difference of only a few numbers (like on the lower settings) you may not be able to predict trends.

Based on the numbers, though, you'd be right - it does look as though the beam profile changes to become more throw as the level decreaes.

Best of luck restraining yourself from buying a U2 /ubbthreads/images/graemlins/smile.gif .

-Brad

Hello Matt,

Very interesting observation...

My U2 seems to have the spill light fall off faster than the central hot spot, which is what Doug (Quickbeam) reported.

I wonder if it has to do with the focus point of the reflector. I remember that early on, there was quite a fuss about the null in the hot spot that occurs when the 5 watter is in perfect focus. The solution was to defocus a little.

My beam has a more pronounce null that what Brad has shown. Doug's beam shot seems to show a bit more null than Brad's. I am not sure how a slight defocus would cause this...

I just measured the difference between the hot spot and the spill just off the hot spot. On high the difference on my U2 shows the hot spot 11 times brighter than the spill, on low the hot spot is 15 times brighter than the spill. This would suggest that there is a tendency towards more of a spot at lower levels.

This is most interesting... /ubbthreads/images/graemlins/grin.gif

Tom

I guess I stand corrected /ubbthreads/images/graemlins/smile.gif. I don't have a lux meter to check as accurately as this.

Perhaps this is something that varies a bit from U2 to U2? Either way, that is interesting to see Quickbeam's figures replicated.

-Brad

The only way the ratio of hotspot to spill could vary with the differing levels is if the light output from the LED is varying across its surface with different output levels.

A very interesting observation, and I haven't seen anyone discuss such a property of the LuxV before.