How to Choose a Flashlight: Lumens, Beam and Batteries Explained

By the middle of September the evening walk starts in daylight and ends in the dark. Most of us grab the phone at that point. It works, right up until you need both hands, the battery sits at 9 percent or you want to see further than the next lamp post. A proper flashlight fixes all three, and choosing one is easier than the spec sheets suggest.

Lumens are only half the story

Lumens tell you how much light comes out in total, not where it goes. How far you can see depends on candela, the intensity at the brightest point of the beam. Under the ANSI/PLATO FL1 standard most serious makers test to, beam distance is where the light has dropped to 0.25 lux, roughly full moonlight. The maths: twice the square root of the candela figure. A 2,050 cd keychain light reaches 90 metres, a 12,293 cd headlamp 222 metres.

The box also will not tell you that the top mode does not last. Compact lights get hot and the electronics step down to protect LED and battery. Fenix states that the PD35R ACE drops a level at 60 °C. That is normal, not a fault. Compare the runtimes of the middle modes, because that is the light you will actually live with.

Pick the size before the output

Same rule as with a knife: the best light is the one you have on you. The Nitecore TINI 3 weighs 20 g on your key ring and still manages 600 lumens in short bursts. It offers a warm 3,000 K that copes better with fog and rain, neutral and cool white, an OLED display with remaining runtime and a lockout, so it stays off in your pocket.

One step up is the classic pocket light of around 14 cm. The Fenix PD35R ACE shows what that class does well: 2,000 lumens, 380 metres, 145 g with battery. The tactical tail switch gives instant on and off, a switch at the neck changes levels, and a hidden SET switch lets you run it with one, three or five brightness levels. Strobe can be switched off entirely.

Built in battery or swappable cell

A built in battery like the TINI 3's is the simplest: plug in USB-C, done. The catch is that empty means empty, and an aged cell cannot simply be replaced.

Removable lithium ion cells in 18650 or 21700 size (diameter and length in millimetres) let you carry a spare. The PD35R ACE charges its Fenix ARB-L18-4000 inside the light and in a pinch runs on two CR123A lithium primaries, which keep for years in an emergency kit. In winter remember that lithium ion loses capacity in the cold, so carry the light in an inside pocket.

Throw or flood

A tight hotspot reaches far but shows you a tunnel. A wide flood lights the trail at your feet and fades after thirty metres. The Fenix LD45R does not make you choose: a 270° rotary switch at the neck moves the beam steplessly from spot to flood, and an OLED display shows output and battery. 2,800 lumens, 480 metres, a 5,000 mAh 21700 battery, IP68. At 302 g it belongs in the pack, not in your jeans.

Headlamps: both hands free

Pitching a tent, changing a tyre, splitting kindling. The moment you need both hands, a headlamp wins. Look for a red mode, which keeps your night vision and does not dazzle the people next to you, and a high CRI mode if colours matter. The Nitecore HC65 UHE has a 2,000 lumen main beam, a neutral white auxiliary light with a CRI of 90 or more for close work, and a red light. 4,000 mAh 18650 cell, IP68, 152 g including headband.

Long range and coloured light

The Fenix HT32 puts white, red and green LEDs behind one TIR lens. White reaches 640 metres at 2,500 lumens, green gives 1,400 lumens and red 400. Fenix builds it for hunters who want to keep their night vision and not spook game with a white beam. The 21700 battery charges on its own USB-C port.

Small things that matter

IP54 covers dust and splashes, IP68 means the light survives submersion. A lockout is worth more than it sounds, because a light that switches on in your bag is empty and hot when you need it. Every few months wipe the threads, grease the O-rings lightly with silicone, and if the light flickers, clean the contacts with a cotton bud and a little rubbing alcohol. And never point a turbo mode at someone's eyes.

The short version

Keys and everyday errands: TINI 3. Pocket light with real reserves: PD35R ACE. One light for near and far: LD45R. Camp, workshop and dark mornings: HC65 UHE. Hunting and long range: HT32.

Browse all flashlights and headlamps, or go straight to Fenix and Nitecore. Building an everyday carry kit? A good light and one of our EDC knives make a strong pair.