How do they come up with a lumens measurement. I have a lite that claims 40 lumens & another that claims 220. Both are about the same brightness & throw about the same distance. How is this possible?

Wow, that's a pretty extreme disparity!

I heard some rumours of a standard for brightness, but I'm not sure where that's at. Really, though, it's all a bit unreliable. Say, for example, you have a couple of lights that use a Cree Q5 LED.

Manufacturer 1 will measure how much light actually shines out the front, once it's bounced off the reflector and gone through the glass front.

Manufacturer 2 will quote Cree's spec for how much light the emitter produces at the emitter, when driven at max power.

Manufacturer 3 will make up something impressive that's just a bit more than everyone else.

Something like that, anyway

Complicating matters is that depending on the reflector or lens, the same emitter can have a broad, bright short-range beam, or a narrow one that projects much further. So, each can seem apparently brighter or otherwise depending on where you're using them.


What are the two lights you have, anyway?

I just got me tactikka xp headlamp by Petzl. It claims a maximum output of 40 lumens. My ultrafire claims 220. They are on par with each other. Slightly different beam, the petzl is a bit wider but both throw about the same distance. I could see how the Ultra could exaggerate a bit(from Deal.Ex). But that is a big difference in #'s.

the ultrafire is guesstimating its output by looking at the spic sheet of the led used and saying "hey this is the max output of this led thats what are lights puting out" but there is little chance that they are driving it to max spic, much less taking into account losses in the light, watch normally add up to about 35%+ of the output of the led, so in all likely hood the ultra fire is putting out some where around 100 lumens (it would help if you said what light you had, there has been testing done on most of them)

The thing is a doubling of lumens dose not mean a doubling of perceived brightness, infact if my understanding is right that you must square the amount of light in order to get a perceived doubling in brightness.

One more factor in that of lux, the point brightness of a light, think laser compared to a light bulb, watch looks brighter? the laser, but the light bulb is putting out vastly more light.

Than you have the fact that the eye adjusts to make everything look the same very quickly, and you end up needing a lot more light in a much more powerful system in order to get that big "wow thats brighter" effect that you where looking for. (fondles sst-50 light)

To compare brightness, do a ceiling bounce test. Point the lights up and alternate between them, see how bright the room is.

Your eyes see light logarithmically, so it would take about 160 lumens to seem like twice 40 lumens. Some light manufacturers rate their lights on guaranteed lumens - out the front, on half-drained batteries. Others measure on lab power supplies, fresh batteried, or outright ignore reflector and glass losses (about 20% on cheap lights). The DX Ultrafire is probably dropping the battery voltage. What type are you putting in?

I also E mailed Mag Industries with this question about a week ago. I gave them a list of my Mags & a story of working in a light sensitive area. Told them I needed the lumen amount & a way to test. They just gave me the output of the listed lights. This is the out the front measurement, with new Duracell batteries. Standard not lithium

1) Solitaire - 2.3 Lumen

2) 2AA Mini-Mag - 5.3 Lumen

3) 2AA LED Mini-Mag(3 watt) - 20 Lumen

4) 4D Standard Mag - 122 Lumen

5) 4D LED Mag - 140 Lumen

Now for my currant line up & how they compare in my eyes.

Streamlight Nano & Keymate - 10 lumens(per packaging).

Comparing to my solitaire & mini-mag, I find this accurate as both are much brighter & throw farther but are not as bright as my Mini-Mag LED.

Uniquefire S10 Cree R2-WC AA single mode - 220 Lumen per ad.

I find this to be way too high to be an out the front #. This is on the similar level as my 4D LED mag. The Mag throws a ways farther so I'm thinking its actual output is more around 100-120 Lumen

Petzl TacTikka XP (head lamp) - 40 Lumen (per packaging)

This is a 3+ mode light. High,med,low & burst. Even low out shines my Mini-Mag LED. On high its a bit under my Uniquefire. With the burst mode it bumps it up & almost doubles the usable light & distance. The Unique still throws a touch farther but the flood on the petzl is awesome. I will be doing a review on My 3 new headlamps from Petzl after they get a bit more use.

Although I never got a true way of testing it gave me some thing to go on. Hope this helps others who may have been wondering the same thing.

I use Energizer & Panasonic(when I can find em). I don't care for Duracell's. They may last a bit longer but the amperage drops off too rapidly & the brightness fades. I have also had problems with them leaking & slowly dying when not in use. I have a P.G.& E(local electric co.) flash light I inherited from my uncle. It is from the 60's. He passed about 15 years ago. I recently flipped on the light & it worked. Good old rusty Energizers inside. That tells me something about their quality. The Energizers fire out at full power till the end. Then just cut out. I like that. But can see how others prefer the dimming effect to use as a battery meter.

Posted by bonnie&clyde How do they come up with a lumens measurement. I have a lite that claims 40 lumens & another that claims 220. Both are about the same brightness & throw about the same distance. How is this possible?

To answer the question we need to look back into history. The modern day word 'Lumen' is really just an abbreviated 'Lou Mens' who was a candlemaker back in the 1800's. At that time his competitor across the street was measuring his light output by the very simplistic 'candle power'.

Lou however wasn't that good at the candle making business. So to try and get ahead of his competitor he created a new unit of light measurement which he could say was brighter than candle power. From his name he created the 'Loumen' and in his advertisements he stated that his candles created 10 Loumens of light but his competitor's candles only produced 1 candlepower of light. Obviously, he said, it'd be better go with a 10 Loumen candle over a single candlepower candle because 10 is more than 1. (even though they were both each a single candle)

Over time though everyone realized that Lou really wasn't really a bight guy and his idea was idiotic. But, the Loumen began to become a common measurement of light all across Europe anyway. Upon hearing of this, England's Royal Body of Scientists determined that even though the scientific basis behind the Loumen was wrong, the word had over taken their society. Still, scientists being scientists had a grudge against Lou Mens whose stupid word overtook science and had become more famous than them. The scientists feared that soon Lou Mens was going to be even more famous than that Isaac Newton asshole. So, they decided to cleverly strip Lou Mens of his fame while still allowing the use of the word for the common people to measure light. They ultimately shortened the word from Loumen to Lumen. That way the Royal Body of Scientists ensured that Lou Mens will never be as bright as the Lumen he created.

So in modern times, that means measuring lumens really isn't worth it since it's based on fake science and while looking for the brightest light, one should actually chose the light which looks the brightest, not one with with the name of some schiesty guy named Lou on it.

Also, I just want to state that this whole post is completely fabricated. There was no candle maker named Lou Mens. There is no English Royal Body of Scientists. I am really really board at work; to seemingly new levels. I have no idea if Issac Newton was an asshole or not. BUT, this was more enjoyable and less mind numbing than clicking the refresh button on uer.ca for the 986th time today. So I wish you the best of luck attempting to get down to the real truth on how many lumens your lights are producing.

-t

Interesting...interesting...interesting...HEY! DICK!

Had me going, had to laugh.

Actually, conveniently enough, I hear Newton really was an asshole.

....wow

HE WAS NOT! issac newton was a freaking cool dude and did a LOT for science and pretend science, he got SOOO close to turning lead into gold....

Also, I just want to state that this whole post is completely fabricated. There was no candle maker named Lou Mens. There is no English Royal Body of Scientists. I am really really board at work; to seemingly new levels. I have no idea if Issac Newton was an asshole or not. BUT, this was more enjoyable and less mind numbing than clicking the refresh button on uer.ca for the 986th time today. So I wish you the best of luck attempting to get down to the real truth on how many lumens your lights are producing.

true dat on the refreshing UER part.. at the rest I lol'd so hard my mom had to come see what I was laughing at. She didnt get the joke. *sigh*

As much as I dislike wikipedia, they have something to say on this topic:

http://en.wikipedia.org/wiki/Lumen_(unit)


And, I called the guys at Surefire the other day to ask why some of their 225Lm lamps only last 1.5 hrs, while other manufacturers 225lm lamps using the same battery power last for other periods of time... even as regulated output.

They said that they, and only a few other companies use very EXPENSIVE sophisticated equipment for measuring output, and the others just use the LED manufacturer's specs, and sometimes pad them a little for advertising purposes.

Posted by Therrin They said that they, and only a few other companies use very EXPENSIVE sophisticated equipment for measuring output, and the others just use the LED manufacturer's specs, and sometimes pad them a little for advertising purposes.

No way! That would be dishonest! A Chinese company just wouldn't do that! Would they?

Posted by Therrin They said that they, and only a few other companies use very EXPENSIVE sophisticated equipment for measuring output, and the others just use the LED manufacturer's specs, and sometimes pad them a little for advertising purposes.

Ah, that makes sense - I remember hearing on CPF recently that those devices are something like $25,000!

A lumen is the measure of the total photonic output of a light, as opposed to candlepower or lux which only measure intensity at a given distance. Lumens are measured in an instrument called an integrating sphere and they can get extremely expensive. I don't know what SureFire is rocking but I wouldn't be surprised if they did spend $25k on measuring equipment for their lights.

As for where the output is measured, at the lamp/emitter or out the front, that's up to the manufacturer. Recently, ANSI and the National Electrical Manufacturers Association got together with a few flashlight companies and put together a list of standards for flashlight performance. You have to pay to view the whole thing, but the overview is free;

http://www.nema.or...202009%20final.pdf