Buying Guide
Lumens vs Candela: Reading a Weapon Light Spec Sheet
You are looking at two weapon lights. Both say 1,000 lumens. One of them will light a hedgerow at 200 metres and the other will not get halfway there. The lumen figure on the box cannot tell you which of the two you are holding — the number that decides it is candela. Once you know how the two relate, a spec sheet stops being a wall of digits and starts describing what the light actually does.
Lumens and candela: what each number measures
Lumens measure total light output. It is the whole quantity of visible light the emitter pushes out, in every direction the reflector sends it. Think of it as how much light there is.
Candela measure intensity in the brightest part of the beam. Manufacturers usually publish it as peak beam intensity. It describes how tightly that light is concentrated into the hot centre of the beam. Think of it as how hard the light is pushed in one direction.
Two consequences follow. First, candela — not lumens — governs how far a light usefully throws. Second, candela governs how well the beam punches through a bright or cluttered background: a hot centre still reads as a distinct pool of light against a lit street or a pale wall, where a soft, diffuse beam of the same total output washes out.
- High lumens, modest candela — a wide, even wall of light. Good for close work and peripheral awareness.
- High candela, modest lumens — a tight hot centre with a dimmer surround. Good for identifying something at distance.
- High both — usually a bigger, heavier light with a bigger battery, and often a shorter runtime.
Not every manufacturer publishes both. Holosun quotes 23,000 candela for the P.ID at 1,000 lumens and 80,000 candela for the RAID, but states no beam distance for either. That is a gap in the published data, not something to guess at: candela cannot be worked out from lumens, and lumens tell you nothing about candela.
Where beam distance comes from
The metre figure on a spec sheet is not measured with a tape. It is derived from candela — conventionally the distance at which the beam has fallen to a very low reference illuminance, roughly the light of a full moon. That is why beam distance and candela always move together on a manufacturer's sheet, and why lumens can jump around without the distance changing at all.
| Light | Lumens | Peak beam intensity | Stated beam distance |
|---|---|---|---|
| Streamlight TLR-3 | 170 | 3,300 candela | 115 m |
| Streamlight TLR-8 X | 500 | 5,000 candela | 141 m |
| Streamlight TLR RM 1 | 500 | 11,000 candela | 210 m |
| Streamlight TLR-1 HL | 1,000 | 20,000 candela | 283 m |
| Streamlight TLR RM 2 | 1,000 | 22,000 candela | 297 m |
| Streamlight ProTac Rail Mount HL-X | 1,000 | 50,000 candela | 447 m |
| Streamlight ProTac 2.0 Rail Mount HP | 2,000 | 85,000 candela | 583 m |
| SureFire M640DFT Turbo (SF18650) | 700 | 100,000 candela | 632 m |
Read down the candela column and the pattern is plain: roughly four times the candela to double the stated distance. The TLR-8 X's 5,000 candela buys 141 m; the TLR-1 HL's 20,000 candela buys 283 m. The TLR RM 2's 22,000 candela gives 297 m; the ProTac 2.0 Rail Mount HP's 85,000 candela gives 583 m. Doubling reach costs far more than doubling brightness. Meanwhile the lumen column does not behave itself — the 700-lumen M640DFT out-throws the 2,000-lumen ProTac 2.0 Rail Mount HP.
Same lumens, completely different lights
The cleanest demonstration comes from one model line. Streamlight builds the ProTac 2.0 Rail Mount in two beam profiles with identical output, identical batteries and identical runtimes:
| Spec | ProTac 2.0 Rail Mount | ProTac 2.0 Rail Mount HP |
|---|---|---|
| High output | 2,000 lumens | 2,000 lumens |
| Peak beam intensity | 17,700 candela | 85,000 candela |
| Beam distance | 266 m | 583 m |
| Low output | 250 lumens / 2,150 candela / 93 m | 250 lumens / 11,500 candela / 214 m |
| Runtime | 2.5 h high / 11 h low | 2.5 h high / 11 h low |
Same headline lumens, nearly five times the candela, more than twice the reach. The extra came from the reflector, not a brighter emitter: the standard version spreads its 2,000 lumens, the HP concentrates them.
The 1,000-lumen class shows the same spread across brands. The TLR-9 Flex gives 1,000 lumens at 10,000 candela for 200 m; the SureFire X300U-A Ultra and M640U Scout Light Pro both give 1,000 lumens at 11,300 candela for approximately 213 m. The TLR-1 HP takes the same 1,000 lumens to 65,000 candela and 510 m — two and a half times the reach from an identical lumen figure.
It runs the other way too. The SureFire X300T-A Turbo makes 650 lumens — a third less than the X300U-A — but at 66,000 candela it reaches approximately 514 metres against the Ultra's 213. Fewer lumens, far more light where it counts. Shop on the lumen number alone and you buy the wrong one.
The headline figure is usually the best case
Multi-fuel lights run on either a proprietary rechargeable pack or disposable CR123A cells, and the number on the front of the box is almost always the rechargeable figure. Drop in CR123As and output, candela and beam distance all fall together.
| Light | On the rechargeable pack | On CR123A |
|---|---|---|
| Streamlight TLR-1 HL-X USB | 1,500 lm / 20,000 cd / 283 m (1 h) | 1,000 lm / 15,000 cd / 245 m (1.5 h) |
| Streamlight TLR-1 HP-X USB | 1,300 lm / 77,000 cd / 555 m (1 h) | 1,000 lm / 53,000 cd / 460 m (1.5 h) |
| Streamlight TLR-7 HL-X USB | 1,100 lm / 23,000 cd / 303 m | 550 lm / 11,000 cd / 210 m |
| Streamlight ProTac Rail Mount 1L-X | 850 lm / 30,000 cd / 346 m (0.5 h) | 500 lm / 18,000 cd / 268 m (1.75 h) |
| SureFire M340DFT Turbo | 650 lm / 95,000 cd / 616 m (45 min) | 350 lm / 55,000 cd / 469 m (1 h) |
The TLR-7 HL-X USB is the one to look at hardest: on CR123A it makes exactly half its advertised lumens and less than half its advertised candela. The M340DFT loses nearly half its lumens and 147 metres of reach. That is the physics of what the cell can deliver, not a defect — but if you intend to run disposable cells, the CR123A column is your light's real specification.
Runtime: the third number nobody reads
Output and endurance trade against each other, and the trade is steep. The ProTac 2.0 hand-held is the clearest example, because it publishes all three of its levels: 2,000 lumens / 17,300 candela / 262 m for 2.5 hours, 570 lumens / 5,000 candela / 142 m for 4.5 hours, or 100 lumens / 890 candela / 60 m for 25 hours. Cutting output by twenty times buys ten times the runtime.
On weapon lights the top-end numbers are short by design. The TLR-7 HL-X USB manages 30 minutes at 1,100 lumens on its pack, an hour programmed down to 550. The compact TLR-6 HL G, 300 lumens on three SL-B2 cells, runs 20 minutes with the LED on. Against that the SureFire M340C Mini Scout Light Pro gives 500 lumens at 7,600 candela for a full hour, and the M640DFT Turbo runs 2.75 hours on its SF18650.
A light quoting a very high lumen figure and a very short runtime is telling you it cannot hold that output for long. Check what it does one setting down, because that is the one you will live on.
What to actually choose
Match the beam to the distance you work at, not to the biggest number on the box.
- Indoors, close quarters, room-to-room. A wide beam with moderate candela wins. Too much candela at three metres is a white-out off a pale wall, and the flood is where you find things at the edge of the beam. A 500 to 1,000-lumen light in the 5,000–12,000 candela band — the TLR-8 X at 5,000, the TLR RM 1 at 11,000, the X300U-A at 11,300 — does exactly the right job.
- Outdoors, open ground, identifying at distance. Candela is the number to buy. Anything from around 50,000 candela upwards puts a usable hot centre out past 400 metres: the ProTac Rail Mount HL-X at 50,000 / 447 m, the TLR-1 HP at 65,000 / 510 m, the ProTac 2.0 Rail Mount HP at 85,000 / 583 m.
- Mixed use. Buy the throw and use the low setting for close work. The ProTac 2.0 Rail Mount HP still gives 214 m on its 250-lumen low setting — plenty for indoors — where a flood-profile light cannot be made to throw at all.
As a rule of thumb — a judgement, not a specification — treat anything below about 10,000 candela as a close-range flood, roughly 10,000 to 40,000 as a general-purpose beam, and above about 50,000 as a purpose-built thrower. Then check what it gives you on your chosen power source, and the runtime at the setting you will genuinely use. Three numbers, in that order.
One honest caveat: this range is built around gun-mounted lights, and the ProTac 2.0 is the only hand-held torch in it. If what you need is a pocket searching torch rather than a light on a rail, you will want to source that elsewhere.
Related reading
Browse the full range in weapon lights, or read choosing a weapon light for mounting, switching and fit. If you are comparing Streamlight models specifically, the Streamlight TLR comparison guide puts the line side by side. £5 tracked UK delivery in 7–10 business days.
