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Dive Lights: Primary vs Backup vs Focus Lights
Divers moving from rental torches into buying their own light system for night, wreck, or cave diving.
The word "dive light" covers three completely different tools. Understanding which one you actually need will save you from spending $400 on the wrong piece of gear.
Three jobs, three tools
Dive lights fall into three functional categories, and a light optimized for one role is actively bad at the others.
A primary light is your main source of illumination on a dive. It needs high output (1500-4000 lumens), long burn time (90+ minutes), and a narrow, focused beam that cuts through particulate. A primary light is the light you dive with.
A backup light is what you use when your primary fails. It is smaller, lower output (400-1000 lumens), and has a wider beam. Backup lights live clipped to your BCD and are only turned on in emergencies or on the last few minutes of a long night dive.
A focus light (also called a photo or video light) is built for underwater photography. It has a wide, even beam to light the subject without hot spots. Output is modest (800-2000 lumens). Focus lights are typically mounted on a camera tray.
For night diving
One primary and one backup. Buy them as a pair. A common mistake is buying a single expensive light and diving without a backup — if it fails at 20 meters on a night dive, you are swimming back in the dark with your dive computer for illumination.
The Big Blue AL1800XP and Light & Motion Sola Dive are popular primaries in the $200-300 range. Any cheap 800-lumen torch from a reputable dive brand makes a fine backup.
For wreck penetration
You need two backups, not one. This is a hard rule in penetration diving: primary + 2 backups. Light failures are more common than you think, and a single backup puts you one failure away from navigating a wreck in darkness.
For wreck diving, consider a canister light (separate battery pack worn on the belt, connected by cable to the light head). Canister lights offer dramatically longer burn times at high output — 3+ hours instead of 90 minutes — at the cost of extra bulk.
For video and photography
Two focus lights mounted on a tray. A single light creates harsh side-shadows. You want to flood the subject from both sides. Pay for good color rendering (CRI 90+) rather than pure lumens — a 1500-lumen focus light with CRI 95 produces much better footage than a 3000-lumen torch with CRI 70.
What not to buy
Avoid no-name Chinese torches rated at "10,000 lumens" for $40. The lumen numbers are invented, the beam quality is poor, the O-rings fail, and the batteries are often unsafe. This is one area where dive-specific brands justify their premium.
- + LED technology means long burn times and no bulb replacement
- + Modern primaries are brighter and smaller than ever
- + Backup lights are cheap — no reason not to carry one
- + Canister lights still rule for serious wreck and cave work
- − Good dive lights are expensive ($150-500 for primaries)
- − Cheap torches from non-dive brands are unreliable and sometimes unsafe
- − Rechargeable batteries complicate travel (airline restrictions)