Recognizing the best features is essential when shopping for the perfect headlamp or flashlight. From brightness to durability, understanding what a light can do helps you decide if it’ll serve your purposes.

However, like with other technical gear, the terms used to measure a light’s performance can feel confusing to beginners. This makes it challenging for you to judge if a light is for you. After all, if a light says it’s IP68-rated and you don’t know what it means, that information isn’t useful.

To help you find the best light for your needs, Fenix has assembled a glossary of flashlight and headlamp terms that’ll help you be in the know. Whether it's your first time purchasing a light or an interesting light feature caught your attention, our reference guide makes sense of words you may encounter.

What Are Some of the Most Common Flashlight and Headlamp Terms?

  • Lumen: A measurement of light output
  • Tail/side switch: A switch on the tail or side of the light that controls on/off functionality and brightness
  • Stride frequency sensor: A feature that adjusts the amount of light emitted to match your movement speed
  • Separate lamp and battery pack: When a headlamp’s lamp is in the front and the battery pack is in the rear
  • Floodlight/Spotlight: Two beam angles that provide a narrow (spotlight) or wide (floodlight) spread of light
  • IP66/IP68-rated protection: The measurement of a light’s protective qualities
  • Hidden port: A feature that improves the light’s waterproof/dustproof rating

Now that you have a fundamental understanding of popular headlamp and flashlight terms, we’ll give more detailed definitions and examples below.



A lumen is a measurement of the total amount of visible light a headlamp or flashlight emits. The higher the lumen rating, the brighter the light. A light with a low lumen output, like 100-300, is perfect for everyday situations such as finding a lost item under the car seat. Higher outputs, like 12,000-18,000, are great for search-and-rescue and tactical operations.

Fenix Flashlights Offer a Range of Lumens

The Fenix LR80R flashlight delivers our brightest lumen output, blasting 18,000 lumens for extreme outdoor activities and long-distance lighting. At the lower end of the spectrum, the E03R keychain flashlight emits a maximum of 260 lumens, perfect for finding your way to the breaker box during a power outage.


A candela is the measurement of a light’s intensity. Different from lumens, which measure maximum brightness, candelas is the measurement of how intensely focused that beam of light is. General rule—the higher the candelas the farther distance a light can be thrown.

Comparing Candelas in Fenix Flashlights

A great example of this can be seen in comparing the LR35R and LR50R. The LR35R can produce a maximum of 10,000 lumens with a maximum candela rating of 63,200. That produces a beam that can travel 1640 feet (500m). However, the LR50R, with only 2000 more lumens (12000 max) has 225,700 candelas, throwing the light 3117 feet (950m) which is over half of a mile.

Tail/Side Switch

TK20R V2.0

Tail and side switches cycle through lighting modes and operate a light with the press of a button. A flashlight may have separate tail and side switches, one for controlling the on/off function and the other for selecting your desired light mode. Lights can also have dual tail switches. The practical purpose of these switches is to operate the light and access its features quickly and efficiently while holding the light in a “tactical” position. And some lights come with only a side switch and no tail switch which allows you to tail-stand the light for hands-free use.

Fenix Flashlights With Different Types of Tail & Side Switches

The Fenix TK20R V2.0 tactical light features dual tail switches for adjusting the flashlight’s six lighting modes quickly. You can tap the tactical switch for momentary on and click the functional switch to find an ideal light mode. The PD25R has a tail cap switch for on/off and momentary on and a side switch on the flashlight’s head for lighting mode selection. While the E28R operates only with a single side switch. Simply hold down the switch to activate the light and then tap the switch to select the modes.

Stride Frequency Sensor

A stride frequency sensor monitors your jogging or running speed and adjusts the lumen output. With this headlamp feature, athletes always have the perfect amount of light to see everything around them.

Fenix Headlamp With a Stride Frequency Sensor

The Fenix HM60R features a stride frequency sensor to light up early morning or evening jogs. While wearing the headlamp, you don’t have to cycle through its nine lighting modes to avoid stumbling into something beyond the headlamp’s spread of light. Instead, the faster you move, the more lumens you have. This intuitive feature adds another layer of convenience to hands-free lighting.

Separate Lamp & Battery Pack

HP30R V2.0

A headlamp with a separate lamp and battery pack usually has a front-facing lamp and a rear-facing battery pack. With this design, the headlamp is better balanced on your head, and, in some cases, you can also use the battery to charge other electronic devices.

Fenix Headlamps With a Separate Lamp & Battery Pack

We designed the Fenix HP30R V2.0 with a separate battery pack and lamp for maximum visibility. The battery case doubles as a convenient power bank for charging your other devices. You can wear the pack on the headband or your waist, or stash it in a pocket or pack. The HP16R also features a separate lamp and battery pack design for a more balanced fit.


Floodlights emit a wide spread of light. The generous spread is well-suited for up-close and medium-distance illumination. On the other hand, spotlights emit a concentrated beam of light for far-reaching illumination, like the kind used for police patrols or search-and-rescue operations.

Fenix Flashlights and Headlamps With a Floodlight/Spotlight

Featuring four white spotlight brightness levels and three neutral color floodlight levels, the Fenix HP30R V2.0 exceeds various lighting demands. The headlamp emits 50 lumens on its lowest setting and 3000 on its highest when both the spotlight and floodlight are used simultaneously. The LR40R flashlight also features an extremely bright floodlight and a penetrating spotlight, which you can use simultaneously for a maximum of 1200 lumens of light.

IP66/IP68 Rated Protection

PD25R rechargeable headlamp

IP stands for “ingress protection.” This global rating shows how well a light withstands water and dust. The first number on an IP rating represents protection against particles and solids, and the second indicates protection from liquids and moisture. By knowing what a light’s IP rating means, you can choose the right one for your needs and know how well the light withstands moisture and dirt.

Fenix Flashlights With IP66/IP68 Rated Protection

The Fenix PD25R’s IP68 rating completely protects it from dust and allows for submersion underwater to 2 meters for 30 minutes.. The EDC flashlight’s aluminum body provides extra protection from accidental drops. We designed the Fenix WH23R headlamp with an IP66 rating that makes the headlamp resistant to heavy rain, splashes, dust, and foreign objects.

Hidden Port

A hidden port insulates a light’s charging interface from dust and water. You access the recharging port by twisting the light, then tighten it again to conceal and protect the interface. One cosmetic benefit of this feature is it maintains the light’s appearance.

Fenix Flashlights With Hidden Ports

The Fenix E09R flashlight features a useful hidden port beneath the head. The concealed interface maintains the light’s IP68-rated protection and removes the need for a rubber-dust cover that can break over time. Our TK20R V2.0 Tactical Flashlight also has a concealed port for charging the battery.

Be a Flashlight and Headlamp Expert With Fenix

The first step to getting the maximum output from your gear is to understand how each feature can benefit you. This Fenix Lighting glossary will help you better understand everyday flashlight and headlamp terms seen throughout our product pages. You may now even see our collection of high-performance flashlights and headlamps in a new light.