Lumens are used as a marketing word for flashlights companies and often, anyone shopping for a flashlight will look at the lumens to decide which one to buy. The manufacturers know this and will tempt you with high lumen output claims.
Manufacturers will sometime use an LED theoretical max output or emitter lumens as the advertised output. This output, though based on something real, isn't real at all. The emitter lumens are just more theoretical numbers based on what the emitter can deliver at the greatest output.
These numbers are not necessarily calculated while in a flashlight, shining through a bezel lens without the loss of the reflector, or are calculated for just the instant they are turned on…then quickly lose 20% or more output within five seconds. Real 'Out the Front' lumens from a flashlight are much lower. Rating the flashlight with emitter lumens will make the flashlight sound incredible but you're not getting this output and the behavior is disingenuous at best.
Starting in August of 2009, the American National Standards Institute (ANSI) approved a new specification standardizing flashlight performance. The resulting specification is called ANSI FL1. The purpose of the standard is to allow consumers to make apples-to-apples comparisons of lights and to eliminate exaggerated light performance by quoting "emitter lumens" or "out-the-front lumen".
There are six criteria used as part of the standard, Light Output [Lumen], Peak Beam Intensity [Candela], Beam Distance [Meter], Runtime [Hours], Water Resistance [IPX Rating] and Impact Resistance. These tests measure, among other things, the real 'Out the Front' lumens for the flashlights being tested. It benefits the manufacturers to sort and choose the best three flashlights to submit for this testing.
With the stated variation in emitter output and driver performance, the luck of the draw can yield several flashlights, from the same batch, that may have much better performance than the rest. So even a flashlight that has been tested to the ANSI FL1 standards may have a large deviation between the officially tested and the light you receive.
All Modlite flashlights are hand built and assembled here in the USA. We take the extra time to test each individual flashlight, not just for function but also light output and thermal regulation. If it doesn't achieve the expected output or meet thermal regulation standards, it's scrapped.
For more information about the ANSI FL1 standard see this link (http://www.led-resource.com/ansi-fl1-standard/)
The photo below shows a flashlight being tested in our integrating sphere.