Lumens, Candela, and Lux

In the last quarter century, lighting technology has progressed by leaps and bounds. Today’s flashlights are generally half the size and offer twice the performance (at least) as the one I perpetually carried as a rookie cop in the late 1990s. Today, there are dozens of flashlight manufacturers with hundreds of models to choose from. The problem that we’re faced with now is that there are too many options.

When selecting a tactical light, there’s a lot to consider: Size, construction, battery power and, of course, functionality. If you’ve purchased a light in the last few years, though, you might have noticed references to lumens, candela, or lux ratings on the packaging. The question is, “Do these ratings really matter, or are they merely a marketing ploy intended to impress the uninformed?”

To answer that question, we need to have a basic understanding of how light works. We often think of visible light in terms of degrees of brightness, but light is much more complicated. Let’s start by defining the terms “lumens,” “candela” and “lux.”

• Lumens refers to the total amount of light emitted from a source.
• Candela is the intensity of the light in a specific direction.
• Lux deals with the amount of light projected on a surface from a given distance.

Lumen is the most popular standard of output used to compare tactical lights, by far. Admittedly, I once bought into the “more lumens is better” hype. Informal testing conducted during departmental range sessions in diminished light seemed to confirm my belief that the higher the lumen rating, the greater the squint factor. Subsequently, the higher the lumens, the more shining the light directly into the officer’s eyes at near point-­blank range negatively affected shooting performance.

The goal of this exercise was to have the officer experience the effects of being “blinded by the light.” This was to encourage the officer to direct light on a suspect’s face rather than on the chest, which is the tendency for many officers. By shining the light on the suspect’s face, the officer can still see hands and the waist area — the most common location on the body to conceal a weapon — but with the added benefit of disrupting the suspect’s night vision. As an aside, when a bright light hits your eyes, shining your own light will restore your vision almost immediately.

Officers dreaded my 1,000-­lumen light, but was it twice as bright as a 500-­lumen light? Not necessarily. Remember, a lumen rating is only a measurement of the total light output at the source of the light. A high lumen output doesn’t guarantee an appropriately configured beam pattern, penetration depth or surface illumination.

Even the lumen rating can be misleading. Many light manufacturers tout a lumen rating that pertains to only potential light. For instance, they may take the lumen capacity of a single LED chip and then multiply that by the total number of LED chips in the unit to come up with the lumen rating. The reality is the actual amount of light a source is capable of emitting is influenced by such real-­world factors as electrical efficiency, lens quality and reflector geometry.

When you’re using a tactical light to illuminate a potential or confirmed threat, the light output that’s theoretically attainable at the lens is far less meaningful than how the beam of light is projected toward the subject you’re trying to see or deter with the light. That’s where candela comes in. To illustrate the importance of candela, let’s look at another drill officers are put through.

In a darkened environment, officers used a flashlight to illuminate a subject at various distances to ascertain what object the subject was holding. This was conducted at various distances and with suspects holding their hands in different locations such as in front of a dark-colored hoodie, a white t-­shirt and so on. Here, candela is critical. You need the beam to penetrate the darkness, not simply flood the foreground with light.

“Candela” is Spanish for candle, and it was historically referred to as “candlepower” because it was based on the attributes of a wax candle of specified composition, dimensions and burn characteristics. A single candle’s luminous intensity is 1 candela.

Candela can be thought of as a light’s “throw,” according to former SWAT team member and low-light shooting instructor Chris Trapp of Shield Spike, LLC. “Your light’s throw should coincide with the deployment capabilities of your firearm. Especially at distance, you need to be able to see well enough to identify a threat”, said Trapp.

Therefore, it makes sense for a law enforcement or military configured rifle to don a light with high candela because there is a greater probability that such a rifle will be deployed outdoors and at a significantly longer distance than a rifle intended for home defense. Conversely, a light designed for interior use needs to be able to flood an area with light, not necessarily project a hot spot down the street. In fact, too much of a hot spot (i.e., too much candela) can create a “wash-out” effect in close quarters, making it more difficult to see.

Candela is also what determines whether your light effectively penetrates ambient lighting conditions. For example, if you’re trying to see what’s in a dark room on the other side of a more well-­lit room, candela is your friend. If the candela level is too low, the light may not be intense enough to illuminate the object or area you want to see.

Of course, when using light to disorient an adversary, the more candela, the merrier. A beam of intense light directed into the eyes can cause a person to reflexively blink or turn their head away. This creates a temporary blinding effect, hindering the assailant’s ability to attack.

An ideal tactical light combines high lumens and high candela, so you get the throw and spill needed to operate effectively at any distance. (“Spill” refers to the dimmer area surrounding a beam’s hot spot). A beam high in lumens but low in candela may work well in close quarters but will have no “reach” downrange, while too much candela will produce an ultra-­focused beam with insufficient spill to see the area around the object that you’re directing the light at.

Although less popular than lumens and candela, lux is quite important because it’s a real-­world measurement of where the beam of light meets the object being illuminated at a given distance. Obviously, beam pattern affects lux, as a tightly focused with minimal spill would result in less surface coverage. Lux helps you confirm a threat. It’s what enables you to distinguish a cell phone from a handgun.

As you can imagine, navigating through manufacturers’ claims of having the “most powerful” or the “brightest” light can be challenging. Fortunately, in 2009, the American National Standards Institute (ANSI) developed the ANSI NEMA FL 1 Standard to mitigate confusion and to establish a standardized testing and rating system. Streamlight, Surefire and several other portable light manufacturers participated in developing the ANSI Standard with the goal being that products could be compared on an apples-­to-­apples basis.

Whether or not you’re familiar with the ANSI Standard, you’ve likely seen it displayed on flashlight packaging. Icons representing Peak Beam Intensity (candela), Beam Distance (lux), Light Output (lumens) serve as a quick and easy references to a light’s characteristics. The terms “impact resistance,” “run time,” “resistance to water,” “waterproof” and “submersible” ratings speak to the overall quality and functionality of the flashlight.

Each company using the ANSI Standard can conduct its own testing if it complies with the established guidelines, or it can hire an independent testing agency. Use of an ANSI icon requires adherence to the ANSI Standard. Manufacturers can’t be selective. One ANSI claim regarding a light product requires compliance with all testing protocols. ANSI icons on flashlight packaging help give the consumer piece of mind knowing they can make an informed decision about which light is best for them.

As you can now see, when selecting a tactical light, lumen output — or the total potential of a light — is important, but so is its intensity (candela) and illumination on the surface upon which the beam is focused from a certain distance (lux).

At one end of the spectrum is a light with high candela and low lumens. This will generate a beam reminiscent of a spotlight. The hot spot is helpful in projecting the beam a considerable distance, but little spill means that it can be difficult to search an area effectively.

On the other side, consider a flood light that’s high in lumens and low in candela. This beam is good for searches in relatively close quarters, but it significantly limits your ability to project your light beyond ambient light as well as use the light to disrupt your adversary’s vision.

An ideal tactical light has high ratings in lumens, candela and lux. So why not opt for the light with the absolute highest ratings in these critical areas? Such light might be more expensive, too large, or may have too short a run time to be a viable option. Or it simply may not be configured to your liking. Thus, there is no “best” flashlight. All you can do is understand the pros and cons of various lights and opt for the one that meets your needs.