After carrying a light every day for more than ten years, here’s the thing I’d tell anyone shopping: you’re probably looking at one number when three of them decide whether the light is any good. Lumens, throw and runtime aren’t a ranking — they’re a triangle, and you can’t max all three at once.
The three numbers, in plain English
Lumens is total output — how much light the thing makes. More lumens means a brighter, fuller picture of whatever’s in front of you. This is the number marketing loves, because it’s the easiest to inflate.
Throw is reach — how far the useful beam travels before it fades into nothing. It’s set by peak beam intensity in candela, and there’s a clean bit of physics behind it: throw in metres is roughly 2 × the square root of the candela. A tight, focused reflector concentrates the same lumens into a narrow column that reaches far. A wide reflector spreads those lumens into a broad, close flood. Same lumens, totally different beam.
Runtime is how long it lasts — specifically the ANSI FL-1 runtime-to-10%: how long until the light drops to a tenth of its starting brightness. This is the number that gets buried, and it’s the one that bit me on my first torch.
Why you can’t have all three
Picture a fixed-size battery — say a single 18650, the workhorse cell in most good EDC lights. The energy in that cell is what it is. You spend it three ways:
- Crank the lumens up and you burn through the cell faster: runtime drops.
- Tighten the beam for more throw and you concentrate output into a narrow column: less spill to see what’s right in front of you.
- Want long runtime? Run a modest, regulated output the cell can sustain — which means fewer lumens.
That’s the trade. A cheap torch pretends it sidesteps the triangle by quoting a peak lumen number it holds for ten seconds. It doesn’t sidestep anything — it just lies about the runtime corner. Honest gear, with published FL-1 figures, shows you exactly where it sits on the triangle.
What daily carry actually needs
Here’s where most people overspend on the wrong corner. Everyday carry is a flood-and-runtime job, not a throw job. Think about what you actually do with a pocket light:
- Find a dropped key in a footwell.
- Read a fuse box or a meter.
- Check under a sink, behind a cabinet, into a bag.
- Walk a dark driveway or path.
- Light up the spot where the dog just went into the bushes.
None of that needs a beam that reaches 300 metres. It needs a broad, even flood so you can see context, a sensible output in the 300–1,000 lumen band that doesn’t blind you indoors, and runtime that lasts the whole job and then some. A thrower — a long-range, tight-beam light — is the wrong tool here. It’ll punch a hot spot onto a fence post fifty feet away while you trip over the thing right in front of you.
Throw earns its keep for specific work: spotting livestock across a paddock, scanning a tree line, search-and-rescue, hunting. If that’s your job, buy for throw. If your job is “see the thing in front of me, every day, reliably,” buy for flood and runtime.
How I’d read a spec sheet for EDC
When I look at an honest FL-1 spec sheet for a carry light, here’s the order I read it in:
- Sustained / regulated output, not peak. What does it hold? A light that holds 600–800 lumens steady is more useful than one that peaks at 2,000 and steps down in a minute.
- Runtime-to-10% at a usable level. I want a couple of hours at a level I’d actually carry on, not a marketing runtime measured at moonlight mode.
- Beam shape. For EDC I want flood or a balanced flood-with-some-throw, not a dedicated thrower.
- Throw (candela) last, and only enough of it. For pocket use, 100–200 metres is already plenty.
A light that nails the first two and has a sane beam will quietly out-perform a flashier torch every day of the week.
The honest version
Lumens get you in the door, throw decides how far you see, runtime decides whether the light is still working when the job runs long. For daily carry, weight it toward regulated output and runtime, with a flood beam — and treat throw as a bonus, not the headline.
I put the carry lights that get this balance right — the ones with honest FL-1 figures and runtime that survives past ninety seconds — into the best EDC flashlights guide. Read the spec the way I do, and you’ll stop buying on the one number that matters least.