ANSI Lumen vs Beam Distance & Peak Beam Intensity

ANSI Lumen vs Beam Distance & Peak Beam Intensity

Flashlight Performance Testing – The ANSI Standard

In 2009, the American National Standards Institute,

in cooperation with the National Electrical Manufacturers

Association, published a standard called the ANSI/NEMA FL 1-2009

Flashlight Basic Performance Standard. The ANSI Standard has

become widely accepted in the portable lighting industry because

it affords a practical way to make “apples-to-apples” comparisons

among different flashlights.

Although the ANSI Standard is not mandatory, Mag Instrument

has chosen to follow it. That is why, on our product packaging,

in our product literature, and on the website, we display certain

flashlight performance data in the form of an “ANSI Strip,” so called

because it uses the officially-designated ANSI logos and reports

data taken in the ANSI-prescribed way.

The ANSI Standard defines four basic performance categories,

and prescribes official logos for displaying results. The following

table lists the categories, and for each one indicates the unit of

measure, the official logo, and the basic meaning of the category:




Light Output versus Beam Distance

Judging from questions and comments we receive, the

distinction between Light Output and Beam Distance is a source

of some confusion. It is important to understand that these two

concepts – Light Output and Beam Distance –deal with quite

distinct characteristic which, surprisingly to many people, don’t

necessarily go hand in hand. A flashlight can have a very high

Light Output (measured in lumens), and yet have a very short

Beam Distance (measured in meters). And the opposite can also

be true: A flashlight can have a very modest output in lumens and

yet can be remarkably effective in lighting up an object very far


Why is this possible? Because Light Output is simply a raw

measure of the rate at which a light source generates light –

i.e., how many photons, how much “luminous flux,” the source

generates per second. It tells nothing about how well or poorly

that light is gathered and directed. Beam Distance, on the other

hand, is a measure of the maximum distance from which an

optimally focused flashlight will cast a useful amount of light on a

target. The ANSI Standard effectively defines a “useful level of light”

by prescribing that the Beam Distance is the maximum distance at

which the flashlight will produce ¼ lux of light. A quarter of a lux

can roughly be described as the light level provided by a full moon

in an open field on a clear night. That’s not as bright as day, but it

is bright enough to see by – a good, standard, working definition

of a “useful level of light.”

So while a flashlight’s Light Output – its “lumen rating” – tells you

nothing at all about how good or bad a job the flashlight does

at forming a useful beam of light, the flashlight’s “Beam Distance”

rating is all about its ability to form light into a useful beam

and send it in a useful direction. “Beam Distance” thus strongly

correlates to a flashlight’s optical quality; whereas Light Output

has nothing whatsoever to do with beam-forming optics. In fact,

to get a high Light Output score, a flashlight would not even need

to have a reflector or lens, at all!

Optics Matter

Since the beginning, Mag Instrument has prided itself on its

beam-forming optics — the quality of its precision-designed and

precision-crafted reflectors, and the versatility of its spot-to-flood

beam focusing mechanism. High-quality optics help a flashlight to

direct light in a useful way without excessive power consumption

– something that the “brute force” approach of maximizing lumen

output cannot do.

Optics and Run Time

High-quality optics can also play a role in slowing battery

consumption and prolonging Run Time. As LED technology

continues to advance, the number of watts of power consumed

per lumen of light generated goes down; but it is still true to

say that the more lumens you want, the faster you will consume

battery power. So it is still true, and probably always will be true,

that excellent beam-forming optics will enhance a flashlight’s

ability to deliver useful light while avoiding the need for enormous

lumen output and correspondingly fast battery drain.



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