I have a bad knee, so I cannot run away in a confrontation. I want to carry a "bright" flashlight for defensive purposes. My question... assuming roughly the same carry size dimensions, what would be the best type of flashlight to carry, that is, which would deter an attacker best... (hypothetically) a 6000 lumen flashlight with 40,000 cd or a 2000 lumen flashlight with 70,000 cd? Am I wrong in thinking the 2000 lumen flashlight would be better? To me, it would seem that the light being directed to the assailant's eyes would be "brighter" (more intense) than the 6000 lumen flashlight. Am I wrong in thinking this? Other than the need to direct what I assume is a narrower beam of light from the 2000 lumen flashlight more accurately, am I missing anything else?
Question on "brightness"... lumens vs candelas
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Lumen83
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Someone way more qualified than me will answer whether that many lumens is more intense than that many candela. However, I would also suggest you consider the real world application at hand. And, ask yourself whether a pencil beam with a ton of lumens vs. a wider beam with a bigger hotspot and spill would be best where there is a lot of commotion, movement, struggle, etc. from both parties. I don't think a flashlight is a great choice for a defensive tool compared to other weapons, but if I lived in an area where a real weapon was not permitted, I think I would want as wide and bright of a hotspot as possible.
StarHalo
Flashaholic
You're overthinking it; anything a few hundred lumens with five-digit throw will be completely blinding to someone with dark-adjusted eyes not expecting it. For a purely defensive role like this, I'd be more concerned with ability to instantly find the power button in the dark, instant access to the turbo mode, etc.
Enderman
Enlightened
The intensity (aka brightness) is completely dependent on candela.
A 6000 lumen 40 000cd flashlight will be just as blinding as a 2000 lumen 40 000cd flashlight because they have the same intensity.
The difference is that the 6000 lumen one will have a larger spot area and therefore easier to aim at the person.
A 6000 lumen 40 000cd flashlight will be just as blinding as a 2000 lumen 40 000cd flashlight because they have the same intensity.
The difference is that the 6000 lumen one will have a larger spot area and therefore easier to aim at the person.
So then I am right... ignoring the aiming question, a 2,000 lumen, 70,000 cd flashlight would cast a more intense light on an assailant's retina than would a 6,000 lumen, 40,000 cd flashlight, correct?
StarHalo
Flashaholic
You need to know the lux, not the candela; if both candela measurements are from the same source/testing, then the 70Kcd light will for sure produce some sort of brighter point of light somehow, but lux will tell you for certain the amount of light falling on a given area at a given distance.
Lumens... candelas... lux... they sure don't make this easy to fully evaluate a flashlight, do they? Nobody seems to post the lux for a flashlight, so... it's off to investigate how lux are calculated. Thanks to Lumen83, StarHalo and Enderman for responding.
By the way, in response to Lumen83's comment about a flashlight not be a good choice as a defensive weapon... I plan to use it to temporarily blind an assailant thus giving me time to pull out my knife (opens quite fast with the flick of my thumb) and finish rendering the assailant unable to complete his attack on me.
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Sounds to me like in the time it takes to pull the flashlight from wherever your carrying, might as well pull the knife first and forget the light. Too much time wasted. Stuff happens in milliseconds in the real world. You should re evaluate your defensive plan... IMO.
StarHalo
Flashaholic
..and that brings us back to the tactical utility of the light being more important than its already overpowering output statistics; almost any of the lights we deal with here would be complete overkill for merely blinding someone not expecting it, but there are plenty that you would never be able to instantly produce from your pocket at max power with mechanical efficiency. Go with a light that is proven for the role, not something with big numbers.
If you are walking in the dark, you may wish to consider having a conveniently-sized flashlight already in your left hand (if you are right-handed). If it is compact enough, have the wrist lanyard already attached to the light and your left wrist. This leaves you free to consider whatever you may wish to plan for the use of your right-hand side. Reverse these suggestions if you are left-handed. Just my 2 cents worth.
Enderman
Enlightened
100% correct.
Candela is lux at 1 meter.
Since he is comparing two lights, this is all you need.
He would not magically move forward some meters if he used light X instead of Y.
He would be using both lights from the same distance, therefore the lux at ___ meters is proportional to the lux at 1 meter, which means it is proportional to candela.
If light X has twice the candela of light Y, then at 398462985 meters light X will STILL have twice the lux as light Y.
Lumen83
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I think this is a good point. And, I think the solution would be to already have the flashlight in one hand while walking around. I could see this as a good use case for a flashlight with a "gas pedal" UI. The user could be operating the light on low mode to navigae the dark and then with a push of the button they would get instant high beam if they needed to use it in the described manner.
archimedes
Flashaholic
Re: Question on "brightness"... lumens vs candelas
Threads on topics of this general sort periodically arise here on CPF, and typically go sideways, then get shut down (sooner or later)
The guiding rule on these discussions here is ...
You agree, through your use of this BB, that you will not post any material ... which promotes activity that ... could reasonably be foreseen to threaten any person's safety
I would like to remind posters in this thread that any discussion of flashlights apart from use as a lighting tool is beyond the scope of this forum.
In other words, no discussion of "weapons" or "blinding" please.
Thank you all for your understanding.
Threads on topics of this general sort periodically arise here on CPF, and typically go sideways, then get shut down (sooner or later)
The guiding rule on these discussions here is ...
You agree, through your use of this BB, that you will not post any material ... which promotes activity that ... could reasonably be foreseen to threaten any person's safety
I would like to remind posters in this thread that any discussion of flashlights apart from use as a lighting tool is beyond the scope of this forum.
In other words, no discussion of "weapons" or "blinding" please.
Thank you all for your understanding.
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StarHalo
Flashaholic
Candela numbers are inflated by spill beam, which the more useful lux @ 3-5m is not, but again it's not relevant in a CQB situation with overpowered lights anyway..
Kitchen Panda
Enlightened
The problem is that we mean so many different things by "brightness" when we use that term, that it's hard to relate that sensation to the numerical measurements.
Measuring light is no harder than measuring liquids. Lumen - the total visible light power. Candela - how much power is passing through a point LUx - how much total light power is falling on an area. It's like "gallons" - how much water in the pool? "feet" - how deep is the pool at any point? "gallons per square foot" - how many walls can I cover with this can of paint?
You could have a narrow pipe going up a hill to a spring - at the bottom, you'd have lots of pressure, but maybe not much water in the pipe. That's like a laser - lots of candelas (intensity) but not much total light power (lumens). An old-timey frosted 100 watt incandescent bulb will fill a residential room with comfortable light levels, but the cat will easily spot the laser pointer dot anywhere on the floor. Lots of lumens, but spread out - lower candelas, and each surface in the room gets a lower lux share.
Stare into a 1000 watt mercury vapor lamp at arm's length, it'll make your eyes water, (because it's so "bright"). But if that same 1000 watt lamp is the only light working in an entire mall parking lot, it's going to be spooky dim when you're more than a short distance away from it. The lumens and candelas produced by the bulb don't change, but the number of lux entering your eyeball goes way down when you're 100 yards from the bulb.
Brightness is perception of light, not an inherent property of any light source.
And what kind of hellish combat zones are people living in that they have to go out armed?
Bill
Thanks all for your comments... and a special thanks to Bill for the above explanation. I don't live in a "hellish combat zone", as a matter of fact, I have never been bothered by anyone let alone accosted, but with my leg problem making running impossible, I just want to give myself the best chance of surviving an attack should one ever happen (better safe than sorry). And left hand on flashlight (for use on someone beyond arm's length), right hand on knife while I walk in areas that could be problematic is what I now do. It is just I saw a new flashlight from Olight (Warrior X) that is only 2000 lumens, but has over 70,000cd a noticeably higher candela rating than my 6500 lumen Nitecore Concept 2 with its 40,000cd rating. Again, thanks all for your participation in this thread... I really appreciated it.
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Enderman
Enlightened
Candela numbers are not inflated by spill.
First of all, nobody measured candela by putting the luxmeter at 1m and taking a measurement, you have to go 10-20m away and take a measurement and then use the inverse square law of light to calculate it back to 1m to get candela.
This is because
A) luxmeters have a limited measurement range that usually only goes up to 20k or 200k lux so you need to be farther away to actually get a measurement
B) luxmeters lose precision when measuring higher lux values so again you want to go farther away to have a more accurate lower lux number
C) depending on the head diameter of the flashlight the beam is usually not fully formed at 1m, that means the luxmeter will not be reading the full intensity of the flashlight
Second, since candela is literally just a recalculation of the lux, you can convert between the two units whenever you want and they will not change.
If a flashlight measured 1000lux at 10m that flashlight is said to have 100k lux at 1m aka 100kcd
So there is nothing wrong comparing lights using the candela value.
If you want to know the intensity at 20m then you just do candela / 20^2 = 250 lux
Third, it is not possible for candela numbers to "be inflated by spill"
The spill also follows the inverse square law of light.
This means it contributes to candela just as it contributes to lux at X meters away.
StarHalo
Flashaholic
..but the reason flashlight reviewers favored lux is because the practice dates from the early 2000's when it was rare to get a light that came near six-digit throw (so it could be measured from any distance,) plus it was always Chinese resellers and LED manufacturers who would publish a cd number instead of lumens, which was not helpful in determining the actual output of the light; seeing a lux value meant someone had actually measured it, though that isn't as relevant now that almost no one is doing light reviews. And it's still not relevant to our hobbling OP who is under threat from people looking to attack the disabled.
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