just purchased an 1800 lumen gun light

the cree XM-L t6 emitter that is in that light you linked according to cree data sheets put out 280 lumens at 700 milliamps, 388 lumens @ 1000 mA, 551 lm @ 1500 mA, 692 lm @ 2000 mA. those advertised lumens are what we call chinese lumens. these chinese light are almost always underdriven(cicuitry not matched to emitter) and have wildly exaggerated lumen claims. lux and more specifically candela(cd) is a good measure of how far a light will"throw".see link in pmack's post. here is some good info from Dr. jones


quote..
Often one can read about "lux" or "lux@1m" to describe 'spot brightness' or throw.

lux is the unit of illuminance E, that is the luminous flux F (lumens) per area A falling onto a surface. It's more a unit for a whole lighting setup onto a target than for a light source itself.

With a single light source like a flashlight, the illuminance E drops with increasing distance d, described by the inverse square law: E is proportional to 1/d² (actually that's an approximation which gets more accurate with increasing distance). If one now multiplies that illuminance E by the squared distance, E*d² gives a constant value, which is independent of the distance and only depends on the flashlight itself. This is another physical quantity, the luminous intensity I, or, measured at the spot, the spot luminous intensity I, or peak luminous intensity I. It's unit is candela (cd; candlepower (cp) is an obsolete unit equivalent to candela): I = E * d²

Of course, one lux in d=1m distance gives one candela, which is why "10000 lux@1m" is somewhat the same as 10000 cd (or better 10 kcd), however the latter is the proper unit. ANSI/NEMA FL1 uses it, too.

Most of you already know that measuring the spot intensity at only 1m distance is not a good idea, as the beam often has not settled to it's 'final beam pattern' in that short distance. Even ANSI/NEMA FL1 demands a minimum distance of 2m; for throwers that is still much too near (I suggest a distance where the spot size is at least 10 times as big as the reflector/lens diameter). Doing so and calculating that back to "lux@1m" sometimes leads to strange units like "31736 lux @1m (calculated)" - just write 31.7 kcd instead.

I just would like to suggest

not using lux when you mean candela
using the "k" for big numbers
not denoting more than three significant digits; typical lux-meters have an accuracy of 5%, a number like 31736 seems to imply a dubious precision of less than 0.1%

While being at it, throw (in meters) is usually defined as the distance at which the illuminance on a (perpendicular) target falls below a certain level; if you follow ANSI/NEMA, that level is 0.25 lx. Throw can be calculated from the spot intensity I using the above formula rearranged to
d = sqrt ( I / E0 )
with E0 = 0.25 lx for NEMA throw. (Some consider that value of 0.25 lx quite low, resulting in relatively high throw values; practical throw values might be lower, depending on the situation.) (more info on throw)

You might find this a bit nitpicking; but I think proper terminology is a good thing, it was developed for a reason.

end quote.
 
I looked on Crees website for the xm-l at 10watts power will produce 1040 lumens. This is supposed to supply 12 watts of power. I also purchased 4000 mah batteries. And the reflector is a smooth polished not an orange peel or plastic. So im hoping it does well. I know the claims of 1800 lumen are false. But im hoping i get lucky
 
Originally Posted By: xxOkieSlayerxx I also purchased 4000 mah batteries.

More mah mean longer run time not more power, you're still only going to get 3.7-4.2 volts. There's a lot of mystery surrounding 4000mah batteries.
 
I own the same brand 4000 mah batteries I use in another light of mine. They are awesome. I know it only means longer run time but it also means more stable current to the emitter as well. This new light uses 2 batteries in series so its working voltage is somewhere around 8 volts.
 
Last edited:
Its states that the xm-l deleviers 100 lumens per watt. So really if it is a 12 watt it is gonna produce somewhere around 1200 lumnens. But the reflector depends on the lux values. If the reflector is crap then the lux values will be lower. I have to similar lights...one uses a smo reflector and the other has a "orange peel" type. The difference is night and day. with The smo reflector I can visibly make out my target at 100-150 yards depending on the moon. The other only about 75 yards. The new light i purchased has the smo reflector. But another factor on reflectors is how "cone shaped they are" i guess you would say.
 
there is no such thing as 4000mAh 18650 size batteries. those are false claims from chinese sellers of fake/recycled or discarded rewrapped rejected batteries. the best/most recent technology batteries as far as capacity are the panasonic 3400 mAh and the actual capacity of those is about 10% less than advertised. the data sheets that i quoted are for the T6 bin emitter in the light you linked to and are accurate and current. the output of the light you linked will be dependant on how hard it is driven. i doubt very much 12watts but hey you might get lucky. most cheap chinese xm-l lights are waaaay underdriven. it does look like a cool light though. i hope it works well for you. i'm not trying cut you down but just help with the facts. i have worked with a few LED's

Picture508_zps45b44351.jpg
 
Thanks man. I'm not mad or anything. I wanted opinions and that's what you gave me. Those batteries might not be 4000 math but I know I use my light every night at work for most of the 12 hours I'm there and it will last like 1 week. Compared to the 200mah that is the same brand which will only last 2 days. I dunno. Hey is there a way i might could put a magnifier type lens in it to make it project further?
 
Just wanted to give you guys an update on the light I purchased. IT IS AWESOME! has a great throw easily can identify targets out to 250 yards with a good scope. Even further in the right conditions! For 50 bucks? I'm sold!
 
Last edited:
With stacked 18650 batteries (7.75 to 8.4v), you will reach out a long ways. The 4000mah batts are BS, I have a few as spares, Best you can get are 3400mah. I pefer the orbtronic brand they test and rate the batts so no false claims.
 
Last edited:
Yes I have recently learned the lies behind any ultrafire or strong fire or trust fire batteries. All rejects that are rewrapped. I just purchased some orbtronics. The ultra fires would limit themselfs out cause this light draws so much juice. The cheapies weren't doing the trick. At least not for very long
 
The orbtronics will do great! I have 4 of the trustfires 2400mah and 2 ultrafires 4000mah they are ok backups, but don't come close to the orbtronics. I'll probably order a couple more orbtronics 3400mah for backups. Keep in mind the lithium cells work best topped off, don't let them discharge too far. The lithium are NOT like nimh or nicads that have to be discharged to get a good charge.
 
Yes super bright. Very well built and lightweight! You won't go wrong with it. With the orbtronic batteries I get a good 90 min continuous and hours just intermittently using it. The cheapo ultra fire "4000" mah would last MAYBE 15 min lol. You get what you pay for. I charge my batteries with the nitecore v2 charger. Great charger and its made in the US
 
Back
Top