The key factors to compare when selecting a flashlight:
Battery type and run time
Size and weight
Flashlights range from under $20 to over $200, yet they may be the same size. What are the differences? Brightness is the biggest one. A pricier light is more powerful due to the use of advanced bulb, battery and circuitry technology. A rechargeable battery can add to the cost, as can features such as strong impact- and water-resistance, effective heat dissipation and multiple lighting modes.
Shopping in person? Check out the following:
How does the light switch on and off? Could it be inadvertently switched on inside your pack? Or, if you plan to use it in cold conditions, how easily could you switch it on or off wearing gloves?
Does it appear rugged enough (or, conversely, light enough) for your needs?
How does it feel in your hand?
Is a tool required to change batteries?
Introduced in 2009, ANSI FL1 standards for flashlights ensure that models are tested and rated in the same way. Compliance with these standards is voluntary and the manufacturers do their own testing, but most major brands now include the following performance data on their packaging.
Measured in lumens. This is a measure of the intensity of the light coming out of the flashlight, on the highest brightness setting powered by new batteries. It may also be shown for multiple light settings. This is a great comparison tool, but does not tell the whole story about brightness. Beam intensity, distance and type all influence the effectiveness of a light in different applications. Light output can range from a modest 20 lumens (great for reading a book) to a terrain-scorching 3500 lumens.
Measured in meters. This is how far the light will shine before the brightness diminishes to the equivalent of the light from a full moon. Full moon illumination is considered adequate for safe and careful travel outdoors. This distance will vary with the brightness setting selected.
Measured in hours. How long does it take the light output to drop to 10% of the rated output on new batteries, rounded to the nearest quarter hour. Light output may gradually decrease over time, or remain largely constant and then suddenly decrease. Run time is commonly given for each light setting. A Runtime graph, if available, provides the best illustration of the performance of a light over time.
Measured in meters. Lights are tested by dropping them 6 times onto concrete at the rated distance. This test is primarily to ensure the light remains functional after occasional accidental drops. It is not a test of resistance for a light being run over, being struck with a heavy object or being used to strike other objects.
Rated using the IPX system. Water resistance is important if using your light in the rain or around bodies of water. Three ratings are used:
Indicates an IPX4 rating, which is splash resistant from all angles, after the impact test has been applied.
Indicates a water submersion rating, also after the impact test.
IPX7 – temporary immersion: up to 30 minutes at a depth of 1m.
IPX8 – submersion: up to 4 hours at the specified depth.
Additional Features and Functions
Some or all of these non-ANSI-rated attributes will also influence your flashlight selection:
Advancements in LED technology have rendered other bulb types almost obsolete. Incandescents such as krypton bulbs still exist in a few flashlight models, but it is hard to beat the energy efficiency, run time, impact resistance and brightness options of an LED flashlight.
The lens reflector that surrounds a bulb influences how the light is dispersed. The 3 common options:
Flood (or fixed): A single beam width. Good for general tasks in camp or while walking.
Spot (or focused): A single beam condensed into a spotlight to penetrate a long distance. This is best for route-finding or other fast-paced activity.
Adjustable: Beam width ranges from wide to focused, or any point in-between. This means, for example, a climber looking for the next pitch would use a spot beam; to study a map, a flood beam.
Lights with a regulated power supply maintain a steady, near-peak brightness level throughout most of the batteries’ life cycle. Near the end, however, light output drops off abruptly and significantly. Unregulated lights start bright then progressively grow dimmer as they drain power from the batteries.
The type and availability of replacement batteries is often a factor in selecting a flashlight.
Disposable: The most common battery sizes in use, AAA or AA, are readily available. CR123A is also a common choice, but is more expensive and can be harder to find. Their upside is a higher voltage output for a smaller size and weight, making possible a brighter flashlight in a smaller, lighter package. Flashlights using D cell batteries are still available if you want a baton-sized tool for security or a light that will not get lost in a pocket.
Rechargeable: Built-in lithium-ion batteries can be recharged through a USB connection from a computer, AC or DC outlet or solar panel. The higher upfront cost is more than made up for by the low ongoing running cost, no need for disposable batteries and reduced waste.
Renewable: Flashlights with a built-in battery energized by a hand crank or solar panel are ideal for emergency kits.
Caution: Do not use lithium or lithium-ion batteries with any flashlight unless recommended by the manufacturer. You risk damaging a light by mismatching it with lithium batteries.
A single setting is sufficient for general-purpose use. Some models offer 2 or more modes like low, medium, high and boost). You may rarely use more than one mode, but having the option to throw an extra-strong beam on demand can be reassuring. The brighter the mode, the shorter the runtime. Some models may offer special modes like a strobe or SOS feature. User programmable modes or mode sequencing may be an option. This may be a feature that is integrated into the flashlight, or set up on software and downloaded to the light via a USB cable.
The type of on/off and lighting mode switches is important for some users. Push buttons and sliders are typically thumb operated. A rotating bezel can also serve as a switch, requiring 2 hands to operate. A safety lock feature prevents the light from being accidentally turned on, helping prevent unexpected flat battery exasperation and inconvenience.
Some lights feature a silent (non-clicking) insta-beam function in which slightly depressing the switch activates the light until either a full click leaves it on, or releasing the switch turns it off, without having to cycle through all modes. This is a desirable feature in law enforcement operations.
Materials and Shape
Most flashlight bodies are either plastic or aluminum alloy. Some feature stainless steel in the head of the flashlight for extra impact resistance. Not all aluminum bodies are the same—thinner styles are lighter, thicker ones are tougher.
Cylindrical bodies are the most common shape, but as these tend to roll around when laid on a surface, some models are profiled to resist rolling. Additionally, the surface of the body may have a knurled pattern to provide grip and reduce slipping.
Size and Weight
This is mostly personal preference. A larger, heavier unit is not necessarily brighter, but it is likely to feature an extended run time due to a greater battery capacity.
Add-ons that may be included or sold separately include a lanyard, belt clip or holster, and lens filters and diffusers to provide lighting options.