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.