When choosing weapon lights – or flashlights, for that matter – there are a number of specifications, details, and so on that, a person should consider, but one needs to be viewed with a jaundiced eye, and that is the output in lumens.
Fair warning: we’re not going to talk about anything sexy, tactical, or even the least bit salacious, so let this be your nerd alert right here.
A potential problem with any datum or measurement, of course, is the method by which it is measured.
Stun guns, for instance, commonly have the voltage output prominently displayed, but the amperage is almost never mentioned, which is stupid since amperage is actually the relevant measurement of electrical current when it comes to efficacy on incapacitating a person.
So while lumens aren’t a totally irrelevant measurement of light output – and we’ll get to that too – they aren’t actually the most relevant for what a weapon light does.
What Are Lumens?
Lumens, in and of themselves, are a scientific unit measuring visible light. Specifically, it’s a measurement of luminous flux, which is the measurement of the quantity of visible light emitted over a given amount of time or distance.
How light output is measured scientifically is broken down into the amount of light produced in what’s called a solid angle, which is the area of the observable field of view from a given point.
In two dimensions, it’s a pie slice with the observer as the apex. In three-dimensional space, it’s a cone-shaped object called a steradian, essentially a conical section of a sphere with the observer at the center of the sphere.
Lumens are a measurement of the amount of visible light across one steradian.
Now, why does that matter?
What this means is that lumens are the measure of the amount of light in a given area. However, the size of the area for standard lumens is undefined; since the area is the amount of light in one steradian or solid angle, the area could be 5 square feet or 5 miles.
Are There Any More Relevant Measurements Than Lumens?
Arguably, two measurements that give you a better idea of light output are lux and candela.
1 lux is 1 lumen of light over 1 square meter. This measurement not only gives you volume but also proportion, a volume of light output but that volume in a defined space.
Another alternative measurement for light that makes a bit more sense than lumens is candela sometimes referred to as “candle power.”
Candela is a measurement of luminous intensity, meaning how bright the light actually is.
The measurement of candlepower comes from the 19th century. While the term is obsolete, the measurement of candela emerged to provide the equivalent measurement
The original candlepower was the intensity of light produced by a pure spermaceti candle weighing 76 grams, burning at a rate of 120 grains (7.8 grams) per hour.
The candela was eventually arrived at as a means of measuring luminous intensity, definable as the amount of light at 540×10¹²Hz frequency, with an intensity of 1/683 watts per steradian.
In other words, the relative power of a light source emitting light (specifically light in the green spectrum, which humans are most receptive to) in a field of view.
So…what does this mean in terms of selecting a pistol light?
Choosing A Weapon Light Based On The Output
So, part of the criteria you want to look at to choose a weapon light is the output. There are other things to look for, of course, but the output is one of the attributes you should be looking at.
Some will have output in lumens, some in lumens, and candela both. Look for candela; the bigger, the better.
The reason why is that while lumens will tell you how much light the weapon light produces, candela tells you how bright it is. And that makes a HUGE difference.
The reason for having a weapon light is both for sighting and for target identification. Therefore, you want the light to be as bright as possible as well as voluminous.
Therefore, besides lumens, look for the highest output in candela as well.
However, not all manufacturers advertise the candela output. The good news on that score is that the higher the output in lumens, the higher the output in candela will generally be as well.