How much overall light a flashlight is generating is measured in Lumens. The light source of the flashlight, LED, incandescant bulb, halogen, HID whatever...has a lumen rating from the manufacturer. They are rated before the light source is ever place behind a reflector or aspheric lens. We all know a flashlight without a reflector is useless as a hunting light. Therefore lumens ratings on hunting flashlights, to a point, are useless.
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.
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 requires a minimum distance of 2m; for hunting lights 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" will yield results such as 20,340 lux. We just write it as 20.3 Kcd. Beam distance. or 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 lux. Throw can be calculated from the spot intensity I, using the above formula rearranged to
d = sqrt ( I / E0 )
with E0 = 0.25 lux for NEMA throw. (Some consider that value of 0.25 lux quite low, resulting in relatively high throw values; practical throw values might be lower, depending on the situation.)
To get a flashlight to "throw" twice as far you need four times as much light.
example:
A typical budget over the counter hunting light puts out about 10Kcd(10,000lux) with a red emitter.
The ANSI beam distance would be SQRT(10,000/.25)=200 meters
Compare this to the T20 which puts out approx 24Kcd(24,000lux)
The ANSI beam distance would be SQRT(24,000/.25)=309 meters
All flashlights follow that basic formula. Hunting lights however are used in very unique conditions. Quite often they are mounted on a rifle or shotgun. Night hunters almost always use some sort of magnification i.e.scope. Looking through a scope at night with a flashlight emitting a red or green beam while trying to identify and shoot a target, presents a very challenging situation. Most common Question...How far can i identify and shoot with your lights? The honest, no B.S. answer is: i don't know. There are too many variables including human eyesight variances, scope quality, air quality(dirt, dust, fog, humidity, snow, rain). What i do know: The beam distance. This is the only true measure of how far a light will throw. In my opinion and experience, most hunters can identify a target with one(1) lux of light illuminating it. So with that said, if you take the square root of the lux, that will give the distance that most hunters will be able to identify and shoot a target at night through a scope. Some hunters have exceptional eyesight and equipment and may be able to identify a target and shoot it with .5 lux illuminating it. In this case you take the square root of the lux divided by .5
Truth in advertising and exaggerated claims:
I believe in truth in advertising. You will not find any exaggerated, or manipulated specifications. In fact quite the opposite, all my data and specifications are backed up by scientific fact, the laws of physics and mathematics. While I could have my field testers and customers post testimonials, I do not believe that is the best way to market my products and services. Testimonials are very subjective and I would not want to mislead my potential customers in any way. For the reasons mentioned above hunter A may get very different results than hunter B.
I get requests for "beamshots" and videos of my lights in action. Any serious photographer can tell you about photography and light. I could easily manipulate the lenses, f-stop, exposure, add light from other sources and other forms of trick photography,etc to help my lights look better than they really are. I will not do that.
My response to the hunter who says"numbers and math mean nothing, how it performs is all that matters". Thats why I offer a money back guarantee, if you don't believe that Spot-On lights are the best performing lights for the money, you have ever used, I will buy them back.
If a light is not rated by the ANSI/FL-1 standard, it is for a reason.
The 1800 lumen XM-L lights and 4000mAh 18650 li-ion batteries DO NOT EXIST.
Batteries:
Lithium ion batteries are the most common battery used in hunting flashlights. With some basic care they will provide a long, safe service life. li-ion batteries must be handled with care. If the cover gets torn the battery could short out causing a fire or explosion. Inspect your batteries regularly for damage to the protective outside insulation. li-ion batteries should never be charged unattended. li-ion batteries should never be over charged. The maximum charge voltage for the kind of batteries we use most is 4.22 volts, 4.18-4.19 is even better. This should be checked regularly with a multimeter. Never trust that your charger is doing what it is supposed to be doing. li-ion batteries should not be over discharged. Discharging below 2.8-2.7volt can be dangerous. Always store li-ion batteries at about 80% charged. or around 3.7-3.8volts. This will prolong the life of the battery. Always use high quality genuine sanyo or panasonic protected batteries. If your not sure what batteries or chargers to use please ask. There are alot of fake, recycled, rewrapped, substandard, unprotected batteries out there. I try to stay up on good sources of quality batteries and i try to have a few on hand for quick delivery in the states.