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Lights - Cameras

Handheld and Canister LED Lights, Strobes and Accessories

Lumens, Lux, Burn Time and Kelvin - Caveat Emptor

Various LED dive light suppliers use different methods of determining light output, plus expressing them in different forms of measurement. What matters is the visible light from the LED that bounces off the reflector and passes through the lens. The quality of the reflector and lens, as well as the actual amount of power delivered by the battery have a major affect on the amount of light that reaches the target. Describing any LED dive light in terms of the specification of the entire output for a raw LED module without reflector and lens at maximum power under laboratory conditions is very misleading. Dive lights would be better described by the system lumens (sometimes called out-the-front or OTF lumens), which is the amount of visible light emitted by the entire system of housing, battery, electronics, diode, reflector and lens.

In our opinion, using lux measured at the target distance (typically 1 or 2 meters), and not just initially but graphed across the entire burn time, is the best way to describe the brightness of dive lights. The difference is that the lux takes into account the area over which the light beam is spread and thus the beam angle. The lux is the visible light measured at the target distance, not the bulb. A light of 1000 lumens, concentrated into an area of one square meter, is said to illuminate that square meter with an brightness of 1,000 lux. However, the same 1000 lumens, spread out over ten square meters, produces a much lower value of only 100 lux.

Some lights appear white or "cool" in color while others appear brownish or "warm" in color. The temperatures in °Kelvin used by manufacturers to precisely describe the color produced by their LED dive light may not be as accurate as you might expect. Dive light manufacturers typically just describe the color of their lights using the technical specification from the diode supplier. However, the actual OTF color can also be affected by the other components the manufacturer used to build the light. We found a helpful discussion with example photographs at Understanding Kelvin and LED Light Color Temperatures.

There is a test standard (ANSI/NEMA FL-1, approved in 2009) for measuring flashlight lumen output, burn time and impact resistance. Sadly, we are not aware of a single dive light manufacturer who has elected to rate their lights using the FL-1 standard. Until they do, we must rely upon our supplier internally published specifications for our descriptions, but we suggest you take all of them with a grain of salt. Like the fuel economy ratings on automobiles, your results for light output and burn times may vary considerably from the questionable values being published by the dive light manufacturers.

Tek Tip Link

Product Spotlight

DGX Gears 700 TWIST Handheld Light DGX 300 Mini Light

8 Lights and Cameras FAQ

Most often the reason is a dead battery plus an error by the diver that causes their handheld "twist on/off" flashlight to flood. The diver twists the light in one direction to activate and nothing happens, so the diver twists the light in the other direction attempting to activate and nothing happens. Then the diver keeps twisting in wrong direction, breaks the O-ring seal and it floods. Other less common reasons are failure to maintain correct amount of lubrication on the sealing O-ring(s); dirt, hair, or salt introduced on the O-ring(s) or sealing surfaces when loading batteries; over-tightening the light head and body together; and finally leaving batteries (especially alkaline chemistry batteries) stored in the light over a long period of time.

There isn't a manual, however there is not much to know. To load batteries in the DGX lights, unscrew the head from the body until the two pieces separate and then insert the battery or batteries in to the body, negative end first such that the positive end will be pointing toward the light head. Hold the head and screw the body clockwise back together all the way until it stops. Briefly push and release the button on the models with a switch to turn the light on or off. To turn off those models without a switch, twist the body counterclockwise until the light goes off then continue to twist the body one half revolution. Once assembled, the twist-on model lights should require a maximum of about one full revolution to turn on or turn off. Do not store any handheld light for extended periods with batteries remaining inside the device because over time batteries can self-discharge and then leak acid.

That's all there is to it, some models also include a little bag of spare O-rings should you need them. There is nothing special about the lubricant, any generic silicone O-ring lube used with underwater equipment will work. If the O-rings ever start looking dry, leave them in place but smear a very small amount of lubricant on the part of the O-ring surface you can see. You might also benefit from reading How to Use a New Twist-On Handheld Dive Light.

Some DGX lights include a generic battery and charger, but any good quality protected-type 18650 battery and charger is suitable for the DGX 600/800 lights. They all pretty much work the same way and are interchangeable. Some batteries ship with a small adhesive cover on the ends, if so remove and discard. Place the battery in the charger, matching the positive and negative indications on the sides of the battery to the same indications on the charger, and then plug in the charger. If the battery is properly positioned in the charger, a red light will illuminate or blink and then some time later change color to green when done. Charging time varies considerably depending on the pre-existing charge level of the battery, typically 3 to 5 hours but can be as long as 6 to 8 hours for a depleted battery, and it's normal for batteries to get warm while charging. Best practice is never leave charging unattended then once the light turns green, unplug the charger and remove the battery.

They are very similar, however the BUTTON version enables multi-function power on (that is not available in the TWIST) offering a HIGH and LOW lumen output and a safety STROBE setting. The area around the button feature is illuminated and will give an approximate battery life remaining notification with color changes.

Most experienced divers prefer the simplicity and reliability of twist-on style lights, but divers can become confused about the twist direction and flood their light. The button-on style light is less likely to flood as a result of user error, but the mechanical nature of the button switch itself is an additional point of failure not present in the twist-on design.

The choice between twist-on or button-on styles is mostly a matter of personal preference, but we do have recommendations for a few specific applications. Button-on style lights are easier activate when used with hand mounts or helmet mounts. If you are mounting the light, we recommend the BUTTON style. If the light is being carried as a handheld backup to a primary, we recommend the TWIST on style. Better yet, if taking two backups for technical diving we suggest one of each style.

For devices that can accept individual standard batteries we recommend purchasing quality replacement batteries through local brand name high-volume merchants such as "big-box" retailers and battery specialty stores. For devices with custom size rechargeable battery packs, such as older canister style dive lights and DPV's, our recommendation is to contact the service department of the original manufacturer to arrange a return authorization. For our detailed recommendations on where to purchase and where not to purchase replacement batteries, read our TekTip titled Replacement Battery Solutions.

The two handheld lights primarily differ in their battery. The bodies of the lights are almost identical in size and also use the same single-die LED with the same 1100+ raw LED lumen rating. Although both lights use a protected lithium-ion rechargeable battery, the 600 uses an a widely available18650 3.7V 3000 mAh battery that requires an separate external AC charger and the 700 uses an uncommon and more expensive 21700 3.7V 5000 mAh battery that contains an internal USB charger. The 21700 battery used in the 700 also better supports high-drain applications; bottom line the 700 has more power. The 700 can drive the LED to produce a little more light than the 600 although we doubt most divers will notice a difference in-water, but more importantly the 21700 battery in the 700 is capable of delivering 50% to 100% more burn time than the 18650 battery. We describe the proven DGX 600 as having a maximum 60 minute burn time, but the newer DGX 700 delivers up to a 90 minute burn time with a gradually dimming but still usable light for another 90 minutes.

Yes, Dive Gear Express continues to offer an expedition quality alkaline disposable battery powered backup light, although all our other backup lights are now powered with lithium-ion rechargeable batteries. Only GUE equipment requirements still say backup lights should be powered by alkaline batteries.

Previous generation halogen and HID bulb primary lights were powered by unreliable NiCad, NiMH or lithium chemistry rechargeable batteries and best practice was to dive carrying two backup lights, both powered with non-rechargeable alkaline chemistry batteries. Today, both high-power LED and next generation lithium-ion rechargeable battery technologies are now well established for mission critical applications. Thus, NSS Cave Diving Section standards were updated in 2020 and no longer require alkaline batteries for backup lights in their training program equipment requirements. TDI and IANTD training standards have been similarly updated to delete reference to battery requirements.

In order to reduce electronic waste, recent changes to regulations in the EU and some other countries now prohibit including external USB chargers (aka power cube, aka wall rat) with products that have a rechargeable battery. In some cases, product descriptions may still mention or depict a USB charger, but it has been intentionally omitted by the vendor and must be sold separately. The original intent was targeted at cell phones but for the products sold globally by Dive Gear Express, this also applies to most of our devices with rechargeable lithium-ion batteries such as: dive computers, gas analyzers, lights, and radios.