So, we all know that you can’t see things clearly at the ANSI throw distance that flashlights are measured at. The question is: how far can you see compared to ANSI throw?
If we can get some typical examples to see how this varies at different distances then we’d have a good guide to convert ANSI throw to visible throw.
I’ve heard the rule of thumb “halve the throw to get the visible distance”. But my guess is that it’s not linear.
Background
ANSI FL1 throw is the standard for comparing how far a flashlight beam throws. The distance is how far the light will shine 0.25 lux on to a surface.
That’s about the same lux as a full moon. You can normally identify things nearby on a full moon and it’s bright enough to hike. 0.25 lux is enough to bounce back off a surface (eg a map) and hit your eyes if they’re a short distance away. When a map 1km away from you is lit up with 0.25 lux then someone at the map will be able to read it but not enough of the photons will make it all the way back to your eyes for it to be visible.
Interestingly, this is also about the brightness where our eye’s cones and rods work together and we just start seeing things in color.
Convert candela to ANSI throw by multiplying by 4 then taking the square root. Eg 250kcd (250,000 cd) times 4 is 1,000,000 and the square root is 1000, so 250kcd = 1000m.
Clarifications
You should be where the flashlight is, not where the object being lit up is
Using mirrors or highly reflective objects (like road signs) is cheating
Measurements will vary due to other variables too. It will be interesting to see how much they vary and of they can be averaged.
Subjectivity of what is “visible”
Eye sight
Weather
Reflectivity
Accuracy of ANSI measurements
General observations from memory or specific measurements welcome. Feel free to discuss other things about throw / candela here too.
I like this, because the ANSI is absolutely useful, but for interpretation purposes figuring this threads main purpose out could be useful for those of us that aren't TOO concerned with on paper numbers, but more about how the light looks while in use. Although, so many factors can change that day to day of course.
Distance at 1 lux is a better measurement for visibility.
Keep in mind that the light has to bounce all the way back to you, so its actually traveling 2x the distance.
0.25 lux is realistically only visible by someone standing at the target, or if you’re pointing the light at a bright object like a white wall and there isn’t a lot of moon light or ambient light around.
ANSI throw rate allows you to compare apples with apples in objective way. What you’ll do with that knowledge is completely different thing, though.
Using 1 lux vs 0.25 or considering 2 x travel won’t tell you whole story anyway, as your night vision is highly affected by spill and, generally, by amount of light in your proximity. And beam shape is not the only factor, but also humidity and diffusion, type of objects illuminated by spill (dark, reflective, leafs moving in the wind and “flashing” etc.), light temperature…
Two flashlights with identical throw rate can give quite different subjective results by spill effect only.
Although I find myself lighting up dark places for coworkers often (only one that edc’s) I don’t do it from far away.
For inspecting things out of reach, like in lrt tunnels or ceilings in warehouses, if the surface isn’t painted high gloss or at all. I’d say to illuminate something enough to find a roof leak or something out of place, 30-40% of the manufacturers estimated throw distance. So like the Olight m2r warrior is 330 meters, maybe 100-150 meters on a concrete surface are really visible.
If it’s a painted or clean surface, the distance would be over half 50-60% of the distance.
In a forest I would say 40-50% of the distance to my eyes. This holds true of Olight, Streamlight, Pelican, Maglite, Klarus, Fenix and FourSevens lights.
I can’t same the same of high cri as the tint sometimes works in your favour while other times works against you at work
They say you shouldn’t cry over spilled milk. You should cry over spilled beer and flashlight spill. Again you have to go back to Martin’s bunker beam shots on YouTube. Whether it’s those tunnel walls in his videos or trees, leaves,bushes, buildings, cars, the ground in front of you, any items that are being lit up by the spill of your flashlight are reducing your ability to see a Target downrange. Less spill is always better. In a lot of beam shots people find positions to get shots where there are no objects being lit up by the spill, but in the real world there will be objects in your field of view in “the spill zone” so the less spill the better. Warmer color lights also help in this regard by not reflecting as much light back at you off of those objects in The spill zone. But they also don’t reflect off of the target as much as cool white does. But I’ll happily take that trade off.
The tir optics in the Acebeam L18 and L19 have a beam pattern similar to LEP lights. If you just want to see what your aiming at, the “spotlight” sort of beam is really useful once you get out past 50-60 meters.
LEP are hands down the most awesome spotlight with next to no spill. If it doesn’t have a low mode it’s not useful for that first 20 meters
I usually use a rule of thumb that a light’s maximum practical range is about equal to the ANSI beam distance in meters changing “Meters” to “feet”. In other words a 200 Meter ANSI beam distance would be good up to about 200 feet. If you wanted to keep everything in Meters, you would divide the ANSI number by 3.28.
Probably a better method is to use civil twilight, which is about 3.2 Lux; to get this you divide the ANSI beam distance by 3.6. Or you can just divide by 4 to make it simple for a approximation.
3.6 is too high though. My Convoy L21B (yes B, new model about to launch for hunters to mount), with the Osram Red has an ANSI spec of 636m which can be seen 370m away on a dark green hillside, easily
If it’s anything like white tail deer, their eyes reflect back the light making them stand out easier. Even light spectrums the animals don’t seem to react to, reflect in their eyes.
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I find what you say to be very true from my use of throwers.
My water cooled light burnt a 6500K led so I purchased a Digi-Key XHP 70.2 5700K, dedomed it, and it performed much better than the 6500K.
Guessing after dedoming it, the color was a little more than 5000K, but you could see more clearly down range. So now I will not purchase anymore 6500K leds.
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I have tried my throwers at many places, but it is difficult to find the perfect spot to see distance and use Google Maps to get some rough numbers. There is always some interfering lights. Took them on vacation to Pensacola, Fl last yr with a spot picked at 1 mile on a yellow building with street lights beside it. You could see the light on the building faintly, but pictures would not take because of the street lights. By the numbers at 1.372,969cd and 2,343m throw or 1.45 mile, it would be short about 30%, roughly.
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This is a very good thread, Thanks Dave 1010 for starting it ! :+1:
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I have decent eyesight but realistically you need an optic to see any detail at night over 100m’s. I couldn’t see a pig & 200m in daylight. But these Osram convoys are making fine light weight hunting setups, if Simon tweaked a few little details he could make one heck of a hunting light for the money.
His new L21B is the same dimensions as the L21A, but weighing in at 210g vs 354g. This is designed mainly for mounting since the cooling fins are minimal making for short bursts on Turbo.
I asked Simon how much it would cost me to get him to design a hunting model for me. The MOQ was 1000pcs, BUT he said he’ll do it for free since he wanted another hunting model. I was so shocked because no company would normally do that. Unfortunately, the focus isn’t as good, but that only drops the range down to 1,250m vs 1,325m which is nothing. If we’re taking the ANSI range and halving it, that’s 35m less.
The center hotspot doesn’t smooth out into the corona so well because of the focus issue, but I’m not disappointed. To be able to get something this affordable which is mountable is awesome. The body is 26mm allowing it to fit into most, if not all, 1 inch (25.4mm) scope rings.
