He’s let his nerd out of the closet again, and today it’s about flashlights. WMLs and lumens, specifically. We’re just happy this new bout of nerdery isn’t about metallurgy issues in the Kalashnikov. 

In a previous post about lights I explained that lumens themselves weren’t the end-all-be-all of a flashlight or weapon-mounted light (WML). Well, they still aren’t, but maybe not for the reasons you’re thinking. I still want bright light; I just don’t want to be lied to or misled.

“More lumens = More Light = More Better”, right? Not quite. How the lumens are measured is important. There are three main ways this is done:

Emitter Lumens: This is the theoretical yield of a given light, using ideal voltage and thermal circumstances, and often tested with a math equation instead of real use. This is why you’ll see a $4 Chinese flashlight on Amazon (a worldwide purveyor of tactical tomfuckery) with a 5,000-lumen rating. The other reason is that they lie about it.

OTF Lumens: Standing for “Out The Front”. That is, the light that a given flashlight actually puts out. Maybe. Because everything in your flashlight is trying to steal the lumens from you. The reflector eats some. The lens eats some. Your batteries won’t always remain at peak voltage. Your flashlight gets hot.

Done properly, OTF lumens are measured with what is called an integration sphere. It’s a device that fully encapsulates a lighting device, diffuses all light emitted, then provides a reading. An OTF lumen rating is certainly better than inaccurate emitter lumen calculations, but could still be wrong regarding use. How? Let’s say you have a 1,000 lumen light but it only pumps out that intensity for 2 seconds before it drops down to 600. A company could still tell you that it’s a 1,000 lumen light, even though it’s much less regarding actual use.

ANSI Lumens: The American National Standards Institute, or ANSI, came up with a testing protocol for measuring lumens. ANSI lumens are also known as FL-1 lumens. It too involves an integration sphere. Testing first involves turning the light on for 30-120 seconds to ensure the LED is warmed up and the battery voltage sags a bit. However, since the testing protocols are known there are ways around it. Many flashlights have voltage regulation built in, and will force a light to step down in intensity if it’s been on for X amount of time. While one could argue this is for thermal regulation (preventing you from starting fires and shit) and to provide a longer and more consistent runtime, there are several companies that have this light step down occur immediately after the 2 minute period required for ANSI regulation testing.

To sum it up: Disregard emitter lumens. While OTF and ANSI/FL-1 lumens can be dubious, you’re best off going with a company that’s worth a shit in the first place. On the same token, just because a light steps down from constant use doesn’t mean it won’t be great for a weapon light. Think intermittent illumination rather than a Coast Guard search and resuce.

As a side note, integration spheres look like time machines from the movies:

More to the Story

While 200 lumens is twice as bright as 100 lumens, it’s not the way we see it. While you’ll notice one light is noticeably brighter, it won’t be perceived as twice as bright. Fechner’s Law states (per Wikipedia) “subjective sensation is proportional to the logarithm of the stimulus intensity. Fechner scaling has been mathematically formalized. In fact, human perceptions of sight and sound work as follows: Perceived loudness/brightness is proportional to logarithm of the actual intensity measured with an accurate nonhuman instrument.”

We are not cameras or precision instruments, and our pupils adjust automatically for a given light source. As such, we perceive light on a logarithmic scale. A difference of 20 lumens isn’t going to make or break anything, all other factors being equal.

Anatomy of a Beam Pattern

Here’s a typical beam pattern of a flashlight. It happens to be the Surefire X300U-A from my CCW handgun. Sizes of each element can and will vary depending on distance to target, lens and reflector design, and yes, lumens.

Hotspot: The focus of the most intense amount of light. For non-adjustable lights it’s tuned for a prescribed distance. The more intense the hotspot, the longer the throw–provided all other factors are equal.

Corona: This is the shifting zone from the hotspot to the spill. It will change in size depending on reflector design and distance to what you’re illuminating.

Spill: Usually nice and even light outside of the corona. With a typical light design as seen above, the intensity is far lower.

Dirty Light: A term I stole from DARC. Dirty light is light emitted outside of your standard beam pattern. As you may recall from your elementary school science class, light consists of photons. Photons have properties of both waves and particles, which means little bits of that dim light goes everywhere–not just what you’re pointing at.

So what’s the difference between flood and spill? The term ‘spill’ is indicative of having a hotspot in the first place. Floods typically shoot light in a wide pattern in a given direction without a discernible hotspot (unless sometimes you’re very close). There are about hundred more terms but those are typically the most useful.

Beam Shots

Just some comparisons of different beam shots with a constant distance and camera settings. I also took the step of taking a ‘top down’ view so you can see how a beam pattern translates at 90 degrees. If one were so inclined they could lay a protractor down.

Surefire X300U-A

TLR-1 C4

TLR-1 C4, Damaged.

This particular light is extremely dirty from gunfire, and also has a cracked lens and broken bezel. Note the effect on both the output and beam pattern.

Surefire X400V-A-IRC

Since this light has more than one emitter (one 350 lumen white light, and one 120 lumen infrared light) the beam pattern is pretty weird. Not bad, just different.

Surefire M600 Frankenstein

When I picked up this M600 it had a dismal 100 lumen head. For the last several months I’ve been trying out an all-flood conversion head. You can still see a hotspot here since it’s so close to the wall, but in actual use it’s just a ton of light dumped out.

 

And an animated version thrown together:

Don’t buy a light only based on all the lumens alone; buy the best light you can for your intended purpose.

-DFM