A19 XRE Beam profile and runtimes

Got my A19 XR-E today and couldn't wait a minute before testing it out. I have not been clear based on the beamshots just how this beam really looked. Based on my data this light
- throws big time compared to other single cell 123 lights
- maintains great output up to about 25 degrees where it drops of sharply.
- is actually one of the more narrow beam angles

This test was done with a RCR123 although output was only slightly less with a primary.

Here's a few runtimes - I show calculated lumens based on the beam profiles. For reference I also show the KL4 hea don the E1L body since that's the only overall competition for lumens output. For the A19 this shows almost a steady/impressive 115 lumens on the RCR123 for about 20 minutes then an abrupt drop. Slightly less output on the CR123 but longer running and no rapid drop.


Pretty decent but I've got to admit I'm a little disappointed in the runtimes as I compare the KL4 head ot the A19 w/XRE. I get about as many lumen minutes from the KL4 as from the XRE albeit at an overall average much lower output.

Overall definitely a quality light with interesting and impressive throw and output over a medium angle beam. But comes with some limitations if you want wide spill beams and/or long run times.

Nice data! :thumbsup: It would be interesting to see a plot with the XR-E driven at 500mA off those cells. Have you tried a beam shaper on the light yet? I would love to see your beam angle plot with such an addition.

lightrod said:

Pretty decent but I've got to admit I'm a little disappointed in the runtimes as I compare the KL4 head ot the A19 w/XRE. I get about as many lumen minutes from the KL4 as from the XRE albeit at an overall average much lower output.

Click to expand...

If you look at the area under the curve, the A19 looks pretty darn close to the KL4.

I took the difference between the A19 and the KL4, indicated in light pink, flipped, mirrored and dropped into the tail area of the KL4 (in dark pink), and there isn't actually that much difference.



A chunk of your power is being lost in the converter used in the A19, fyi. It is the nature of many Buck-Boost that you loose a bit of efficiency, to have both buck and boost in the same circuit.


BTW, nice beam profile stuff!
.

The area under the curves - what I call "lumen minutes" although not sure it's the right term - is in fact just about the same: 2400 for the A19/XRE, 2600 for the KL4, over the one hour period on the plot on the RCR123's. However the actual average output during the period that the battery is draining is 115 lumens for the A19 (over the 20 minutes - this puppy is either big time on, or off) and 43 for the KL4 (over 60 minutes). I suppose other things equal however you'd expect more efficient LED operation at the lower outputs so the KL4 should be significantly higher in lumen minutes than the A19. Since it is not, then I'm taking it that the A19 is in fact quite a bit more efficient. Does that make any sense guys? Anyway enough rambling on that - a very indirect way to infer efficiency! I do not have the means to drive these at various currents.

I added profiles for both the KL4 and the A19 using the SF F4 diffusion filter - the only thing I have to try. Big impact as expected. Interesting but not totally surprising that the KL4 and A19 beams become quite similar using the F4 (although directionally the same in that the KL4 has less throw and a wider spill).


BTW - the diffusion filter reduced overall output (lumens) in both cases: the KL4 by 20% and the A19 by 10% (not sure why this would be different / not sure I'd hang my hat on those numbers either - let's call it about 15% overall).

Incidentally - since I have the pros on the line here, I have come up with what I consider an ideal "walking beam profile" and would love your input. This profile, when holding a light at shoulder level and angling down about 5 degrees has several nice features:

• provides very uniform ground illumination (lux) levels from about 1 meter in front out to about 10 meters
• maintains relatively even illumination as the light angle is varied several degrees either way
• does not have a "hot spot" that blinds you if angling the light down significantly, e.g. to illuminate the ground at your feet

I've plotted it for reference below against the KL4 and the A19 beams (forcing the walking beam profile to provide just over 100 lumens as the other beams do). The walking beam profile is close in some areas to the KL4 pattern (which is by far the best such walking beam I know of), but is much superior still in terms of the attributes above.

My question is whether it is (practically) possible to design a reflector or optics to provide a specified beam profile. I think this beam would be the bees knees for general use if it were possible. And with higher power available as with the XRE I envision a two level light with about 20 lumens for general use, then with access to ~150 lumens only a tailcap push away you could still get decent throw when needed - and what a light curtain it would be - I'd be the first one in line!!

Are you saying that although the runtime is slightly shorter for the A19 than the KL4, that there is much more total lumens output by the A19?

I have an A19 and a TW4 and although the A19 is brighter, its not
overwhelmingly brighter to my eyes - although I realise that the brighter the output becomes, the harder it is to discern the difference.

It would be helpful if you stated the type of converter in your A19. Is it a BB, Wiz2, what bias?


With the Cree's, there's no need to go balls to the walls on drive level IMO. For a practical light 500mA is plenty and with the Cree's efficiency, you will still get a very bright light.

easilyled said:

Are you saying that although the runtime is slightly shorter for the A19 than the KL4, that there is much more total lumens output by the A19?

I have an A19 and a TW4 and although the A19 is brighter, its not
overwhelmingly brighter to my eyes - although I realise that the brighter the output becomes, the harder it is to discern the difference.

Click to expand...

I see the same easilyled - the KL4 at it's initial/top output is not much different in total output visually than the A19. The KL4 clearly has less throw but equally clearly more flood. Both very impressive in their overall output - the beams just place the output in different areas and there's not much difference overall to notice practically.

All I'm saying (and I do not think it really means much BTW - just an observation and in fact all pretty confusing probably!) is that the AVERAGE output of the KL4 over the one hour period of running down the battery is much less than the AVERAGE output of the A19 during its (much shorter) period of running down the battery. If you compare the output at the starting point it's not that much difference in actual lumens or IMO in visual gauging of output.

Okay, so if I look at your chart, the A19 is 4.6 times brighter than the KL4 at the center of the beam profile (spot), and it continues to produce more light than your KL4, clear on out to 25 degrees, or a 50 degree beam angle from side to side (flood area). I am reading it correctly, yes?

Beyond 50 degree beam angle, in the KL4's extreme flood area from 50 degree beam angle to 90 degree beam angle- where the light output for the KL4 drops to 1.5% of the center beam brightness of the A19, then KL4 is brighter than the A19 in the extreme flood area.

I see what you're saying lightrod - thanks for clarifying.

One would indeed expect much more lumen-minutes from the A19-XRE
since the emitter is supposed to be twice as efficient.

Maybe this is due to a combination of factors such as:-

1) inefficient buck-boost converter
2) heat-sinking not comprehensive enough
3) less than optimal drive level at 825ma

but I'm only guessing.

Terrific concept, measurements and graphs - I'm in awe.

A light held at waist level needs a less wide beam to illuminate the ground from one meter to 30 meters out, than does a light held at sholder level, although the amount of light reaching the ground at various distances will vary more (assuming the same total integrated frontward output for both lights). Although I appreciate the advantages of "hands-free" illumination, I prefer to eschew headlamps, and to hold my light at about waist level, to avoid attracting bugs to my face. Does anyone else feel the same way about that?

Blinding close-up hot spots might be avoided by using a secondary, lower output level - if you have one.

The "ideal walking beam profile" - great concept and object of comparison!

NewBie said:

Okay, so if I look at your chart, the A19 is 4.6 times brighter than the KL4 at the center of the beam profile (spot), and it continues to produce more light than your KL4, clear on out to 25 degrees, or a 50 degree beam angle from side to side (flood area). I am reading it correctly, yes?

Beyond 50 degree beam angle, in the KL4's extreme flood area from 50 degree beam angle to 90 degree beam angle- where the light output for the KL4 drops to 1.5% of the center beam brightness of the A19, then KL4 is brighter than the A19 in the extreme flood area.

Click to expand...

Yes that's absolutely right.

Noteworthy here (and old news to most I'm sure) is that the brightness in the beam center - say from 0 to 5 degrees - does not carry much weight in terms of overall light output (lumens) since the central few degrees of the beam profile covers a relatively small area when projected out a given distance. For example, there's about 3 times as much area covered by the projected beam from the 5 to 10 degree portion as compared to 0 to 5 degrees; at 30-35 degrees there is over 12 times the projected area covered by the beam than at 0-5 degrees. It takes a lot of light output to brighten the area above 30 degrees such as the KL4 head. ALthough it may appear from the plots that the A19 "crushes" the KL4 overall since it's so much more ouput in the initial 25 degrees or so, the KL4 almost "catches up" by having more much more output from 25-50 degrees.

It is for this same reason that outstanding throw can be obtained with relatively little output - that is as long as most all of the output is concentrated in a very central angle (tight spot) which then spreads to cover only a very small area when projected in the distance.

Personally, I consider throw, at around a maximum of 5 degrees beamwidth, or 2.5 degrees in your chart.

Beyond that I consider corona, out to around 10 degrees, or 5 degrees in your chart.

Then there is flood which runs out to 25 degrees, or 12.5 degrees in your chart.

Then from 25 to 50 degrees, 12.5 to 25 degrees in your chart, I consider spill or very wide flood.

Beyond that is just left overs.

But this is considering a light with throw.

Your poor little R123A cell is getting slaughtered by the KL4's obscene current draw. You shouldn't have a runtime profile like that for a li-ion power plant. I'd like to see the same runtime chart where both the A19 and the KL4 are powered by a much more capable li-ion cell, such as a 17670 or an 18650.

martonic said:

.....A light held at waist level needs a less wide beam to illuminate the ground from one meter to 30 meters out, than does a light held at sholder level, although the amount of light reaching the ground at various distances will vary more (assuming the same total integrated frontward output for both lights). Although I appreciate the advantages of "hands-free" illumination, I prefer to eschew headlamps, and to hold my light at about waist level, to avoid attracting bugs to my face. Does anyone else feel the same way about that?......

Click to expand...

I agree that waist level can be a good holding point - for me it's not so much the bugs as it is the fog. Doesn't matter much on a clear night but any fog/mist/rain and waist level works a lot better.

The proposed "walking beam" maintains its advantages when the light is held at 1 meter (waist level) instead of at 1.5 meters (shoulder level). As you rightly point out the local ground illumination becomes brighter overall (about 2x in fact) at 1 meter, but uniformity of the resulting ground illumination from 1 meter to about 10 meters, across a range of angles, is still quite good compared to other available beams.