Measuring the brightness of a diving light's beam as it falls on a fixed point at the bottom of a swimming pool (left).
Light output was measured with a submersible photo-electric meter at the centre of each lamp's 'hot-spot'. From our meter readings, we then produced brightness values, ranging from 2 upwards, for each lamp. Thus, a lamp revealed as having a brightness of "100" can be considered to be five times 'brighter' than one with a measured brightness of "20".
However, brightness can be a bit of a red herring. This is because the human eye has an excellent light-sensitive retina armed with rods and cones, enabling us to see well in a wide range of light conditions. It is only when diving with a buddy with a much brighter lamp that any discrepancy in your own lamp's light output will show up. So the brightest light tested here might not necessarily be the best for you.
Size matters. This picture (right) shows the relative sizes of a typical torch, mini-torch, lantern, oversize lantern and technical light.
The brightest lamp was more than 1000 times brighter than the least powerful, yet both will allow you to see in the dark!
Some lamps had a very tight hot-spot, others a broader one. Some also had a usable peripheral halo; where this is significant, we give additional figures for overall width including halo.
A broader beam is not always ideal. A bright broad beam can turn a night dive into daylight, but a narrow one can be more selective and does not wake the fish before you reach them. Those exploring wrecks often prefer a broad beam to avoid missing anything. It is a question of choice. Only one lamp reviewed, a Subatec, provided an even enough light to be used for video.
Some lamps revealed a particularly patchy beam, and this is less than good. Where we encountered them, we name the offenders.
In poor visibility you need to be able to hold a lamp away from you so that you don't look along the axis of its beam, lighting up detritus in its path. Head-mounted lights, which evolved for cave-divers, are less useful in these circumstances and also attract any plankton around them! They will temporarily blind your buddy when you look at him, so are best suited to solitary divers working in clear water.
Most of the lamps tested were negatively buoyant. This is convenient because when clipped to a lanyard they will hang down and be easily found. Some heavy torches were extremely negative, and could prove a problem if included in a diver's weighting configuration and inadvertently dropped - the lamp goes down as the diver goes up!
This is not a problem if the battery pack is attached by a belt or to the tank. However, the prudent diver will check that his BC will provide sufficient buoyancy for the complete rig before jumping off the boat!
Some lamps seemed to be almost neutrally buoyant in seawater. This was found to be true of several of the lampheads fitted with umbilicals to power supplies. Others were positively buoyant, often unwelcome for divers.
Readers might be surprised at the wide price range. Because any item with an airspace taken underwater is likely to flood and fail at some time, we recommend that you divide your resources between a number of lights, so that you always have at least one back-up when you need it.
|ALS Marine||01797 227185.|
|Aqua-Lung UK||01162 251 4200.|
|Blandford Sub-Aqua||01923 801572.|
|Birchley Products||01452 380448.|
|Custom Divers||0181 644 3393.|
|Eurotek Communications||01895 236446.|
|Northern Diver||01257 254444.|
|Oceanic SW||01404 891819.|
|Robin Hood Watersports||01924 443843.|
|Sea & Sea||01803 663012.|
|Scubapro (UK)||01256 812636.|
|Solent Divers (Portsmouth)||01705 814924.|
|Terry Swanborough Diving||01964 532202.|
|Submarine Manufacturing and Products||01772 687775.|
|UWI Circle||01420 544422.|