Aleph runtime comparisons?

[Halibut]

I've been looking at the runtime graphs on Don's Web site and am curious.

The KL1 graph that appears here shows a lux reading that's comparable to that of a Nexgen 1000/Aleph2/TWOH . Is this even possible with a stock KL1, or do I err by making direct comparisons between two different graphs?

Also, the lux readings for the Nexgen 400/500/Aleph2 are pretty close to those from the Nexgen 1000/Aleph2. It almost seems like a waste of juice to go with the higher current, doesn't it? /ubbthreads/images/graemlins/confused.gif

-Dan

 

[McGizmo]

Dan,
The KL1 is the new KL1 and it is brighter than the Aleph 2, ceterus paribus but don't forget that the optic in the KL1 is putting all of the light in a moderately tight spot with no spill whereas the 20 MM reflector gives you a larger spot as well as a spill beam. Different animals completely!

I want to try to find the time to measure Lux VS current of a LuxIII at one meter behind the same reflector to illustrate that you really pay a significant price for the extra lumens when it comes to power! The significant thing to keep in mind that the power that is NOT being converted into photons is all additional heat that requires management! The real beauty in all of these LED's is the increased efficacy when they are driven at conservative or even low levels! I agree that there are needs for illumination tools that reach out and touch a distant target but to use a poor analogy, there are many on CPF who are using gas guzzling "muscle cars" to run errands on city streets!

Unfortunately, many of my run times are using different LE's with different LED's so the differences in lux and drive currents are likely skewed considerably!

 

[Chop]

Halibut,

It's tough to compare two lights by looking at a graph. The beam characteristics of the new KL1 are, what I would consider, special purpose. It shoots a beam of light, like a laser. I find these beam to be pretty useless, especially if I were trying to find something in the dark and had no idea where it was. With the KL1, you could quite literally pass within a foot or two of what you are looking for with the beam (hotspot) and miss it.

This beam put out by the new KL1 is nothing new, although the Surefire way of doing things appears to be really efficient. Not too long ago, the Fraen LP was all the rage because of the BRIGHT hotspot that it put out, at the expense of all sidespill. Well, that fad died pretty quickly. I had a box full of Fraens that I removed and replaced with reflectors. I almost had a hard time giving the Fraens away.

OK, I'm getting long winded here. The short of it is that the graph is misleading. All the lux number tells you is that the focus (central hotspot) of the beam of the KL1 is brighter, but what it doesn't tell you is that the hotspot is all you get. You don't get the utility beam that you get with the Aleph.

Some of the smartest lights that you could buy right now would probably be a stock older KL1 with a HD and reflector, an Aleph II with a Nexgen biased for around 400mA, or anything else that runs on a conservative current level. Why do I say this? Because these lights will be TRULY USEFUL in 90% of the applications that a flashlight is used for. I mean this in terms of brightness, runtime and heat.

 

[Roy]

I think that this picture demonstrates why you shoudn't compare the vertical axis of a runtime plot.

Notice how much light is NOT being measured. Remember that the main purpose of a runtime plot is to measure TIME.

 

[McGizmo]

OK,
I took a break fron the schedule and did a simple test. I set a E-Screw with Lux III in a beefy *special* McR-38 host and direct drove it off my variable power bench supply. The Light was clamped 1 meter from the light meter and rigid during my testing where I would vary the current limit to the LED and measure the resulting Vf as well as lux:

I'll let the math experts play with the numbers and tell me where I have errored. /ubbthreads/images/graemlins/tongue.gif

To explain the last three columns, take for example the 3.56 Vout row (700 mA). The percent deltas are figured from the increases in the watage and lux going from the levels at 3.49 Vout to the 3.56.

In going from 215 mA of current to 312 mA of current, The power was increased by 50% wheras the lux increased by 33% or to normalize, a 100% increase in power would see a 66% (65% by the chart) increase in lux. 34% of the power at this level would be wasted as heat.

When you get up to 700 mA and continue to increase power, 50% of the energy will go to light and 50% will go to heat.

Now the returns obviously diminish as you go up and provided the thermal relief of the system is adequate or the light is used in short blasts prior to thermal saturation, you may well choose for more light over diminishing efficiencies. However, if the system is not up to the thermal load, for whatever reasons, as the temp rises, the lux will drop.

If the illumination tool needs to be used at or near its limit, then there may be no choice but to go for as much light as possible regardless. However if the tool is being used well within its range of effectivity, a strong argument can be made for driving the LED at much lower levels. /ubbthreads/images/graemlins/icon3.gif

Note: the heading on the last column should be %^Lux / %^Watts where I am using ^ to signify delta or "change"

 

[Chop]

Is that right? 3300 lux at 500mA? Geez, you could get an Aleph II with a nexgen500 for almost two hours of runtime on a sinlge 123 and throw an Aleph III head on it to really reach out.

OK, sorry to go off topic, but that 500mA number has been stuck in my head for some time now. It's kind of like a break even point where increasing performance is really gonna cost you in terms of runtime and heat. Especially in the context of a single cell light.

 

[Halibut]

Yowzahs. Incredible info, Don and Tony--greatly appreciated!

Don, can you put that chart on a sticky post?

-Dan

 

[McGizmo]

Dan,
If I can find the time and energy, I think I am going to put together an Aleph Factoids thread that will be a sticky and locked so it stays clean. /ubbthreads/images/graemlins/thinking.gif /ubbthreads/images/graemlins/icon3.gif

 

[Chop]

Halibut,

I'm just puking up something I heard someplace else.

 

[Kiessling]

A very reasonable combo, too:

Aleph2 / Wizard2 520 / 2x123

At 520 mA plenty bright for almost everything except that noise in the tree over there ... and the runtime is gorgeous:

... AND it can also run on 1x123!

bernhard

 

[Doug S]

Very nice, Don. It clearly illustrates the points that you have been trying to make for awhile. I won't comment on wacko statements like "50% of the energy will go to light and 50% will go to heat that are goofy if taken out of context.
/ubbthreads/images/graemlins/nana.gif
I suspect that folks will know what you really meant. /ubbthreads/images/graemlins/grin.gif

 

[this_is_nascar]

[ QUOTE ]
Roy said:
I think that this picture demonstrates why you shoudn't compare the vertical axis of a runtime plot.

Notice how much light is NOT being measured. Remember that the main purpose of a runtime plot is to measure TIME.

[/ QUOTE ]

... and it for this exact reason that I choose this method to perform my comparitive testing. Using this method (in a fully darkened room) really gives a good comparitive plot of not only runtime, but how much light is coming out the front of each test unit.

As soon as I receive my Aleph-2, I'll do a test similar to the rest.

 

[Miciobigio]

Ray,

you are right , but using your test you don't have a measure of how bright is the hotspot , an "only flood" flashlight can have similar output graph ( using your test ) of a "throwing flashlight" with a very bright hotspot and a dim side-spill.
Or am i wrong ? /ubbthreads/images/graemlins/help.gif

 

[McGizmo]

Ray's test is based on flux (lumens) and not lux (throw). Both are valid for runtime analysis but both only tell "part" of the story.

 

[this_is_nascar]

Agreed.