Check out the full comparison with an interactive comparator and a graph viewer:
And yes, I do have an L21B F150R on the way. It will receive its own special comparison against other emitters when I get it.
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Nice! The LHP351 would be a nice comparison also. Do you have one?
The LHP73B is not included on the combined graph, was that on purpose? I am curious how it would compare to the sft90 for heat and sustained output.
Yes, I mentioned so in the full post on my website. The BLF post doesn’t have any of my commentary.
I didn’t add in a LHP73B runtime, as I sadly only have it in a L21A, which has different thermal characteristics compared to the L21B, but the same beam.
Comparing L21A and L21B together thermally wouldn’t be fair. But if you want to see the L21A runtime you can just use the interactive comparator and the graph viewer.
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Minutia here, but I think it’s interesting to see how you define realistic flashlight throw.
I’ve always said take the ANSI throw and divide by three for a realistic distance, and that’s how I evaluate flashlight purchases to see if they’re going to be suitable for what I want the light for. I wonder if ANSI/3 is works for most people.
From my own observations, dividing by 3 seems to work best to give a realistic maximum range at which the flashlight is still effective. Divide by 2 for larger or more easier to see (more reflective) objects like buildings, larger vehicles.
For example here’s a flashlight with 230m of ANSI throw. Dividing by 3 gives 73 meters. A photograph doesn’t fully express how much visibility a flashlight provides, but seeing how to the end of the path it’s 50 meters, the estimated max range by dividing ANSI by 3 seems to give a realistic expectation.
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Sadly I don’t have one with a LHP351
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This is a pretty good heuristic in my experience too, at least for most lights we encounter. Assuming no atmospheric scattering, 1/3 ANSI distance is equivalent to 2.25 lux on target.
With extreme throwers, atmospheric scattering becomes significant. This discussion actually motivated me to learn more about it and make a usable distance calculator that accounts for atmospheric losses: Calculator for usable throw
For example: if a light has a ANSI range of 3km, then your heuristic (2.25 lux on target) gives 1km of usable range under ideal conditions. If the air quality isn’t so great with only 10km of visibility, then the observed illuminance drops to 2.25 lux noticeably earlier, at 747m.
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Im living this right now. I’ m camping on a lake shore. Its probably 250 yards to the opposite shore. My 550,000 cd SBT90.2 thrower does not make it across. It looks clear, but when i turn the light on it’s apparently soup.
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Nice
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This +1
I’ve found that numbers don’t always add up to real-world usability. You can have a measured, confirmed 1500 meter capable thrower, but a 900 meter target (that’s white, no less) is barely illuminated on a somewhat dark night by the naked and aided eye. It takes a 2300 meter thrower to really light it up to the point our eyes can perceive it as “bright.” It would be cool to have a formula to plug your candela number into that would give you the theoretical perceived candela at a goven distance (like 50 m, 150 m, 300 m, etc).
Part of this might be due to atmospheric scattering. Assuming perfectly clear air, a 1500m thrower should produce 0.69 lux on target at 900m. But with worse conditions (say 10km of visibility), the target only receives the equivalent of 0.34 lux to the eye of the person holding the light, which is less than half of what a naive calculation predicts!
Here’s a calculator that does it and takes atmospheric scattering into account. Usable range calculator | Desmos
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