DIVER TESTS
Let there be light!
Testing lights No, it isn't a human Christmas tree; it's Diver's Managing Editor Steve Weinman, all dressed up for a dark night in the interests of our latest survey: Everything You Always Wanted to Know about Diving Lights, but Had Nobody to Ask. Now you have: it's John Bantin
Underwater lighting is an essential part of any diver's equipment. In the less than perfect conditions found in our home waters, a light will show the way, indicate your position to your buddy and, in worst-case visibility, allow you to decipher the readings on your gauges, computer, compass or watch. In what Julius Caesar called a "land of mists and fogs", a light held on the surface can also aid cox-swains to find divers caught by weather that has clamped down while they were under the surface.
Even in the fabled gin-clear conditions found "abroad" - but not always - a good underwater light can be essential. Looking into holes and cavern mouths, investigating wrecks, discovering the true, vibrant colours of flora and fauna by shining white light closely at them; all are good reasons for entering the water equipped with a good light.
Then there is the magic of diving during the hours of darkness! This is when one light per diver is certainly not enough. Whenever no ambient light is available, every diver should be equipped with a reliable back-up light source.
Reliability is the key word. Underwater lights are usually very low- tech in design and tend to be overlooked and abused by their owners. Too often diving torches flood, batteries are found to be near exhaustion or inadequately charged, or bulbs blow.
Clean and lubricate the O-rings of your torch just as underwater photographers nurture their expensive cameras. Monitor burn-time of dry cells and never mix new and used batteries. Recharge ni-cad cells or lead-acid batteries before diving (that old chestnut of ni-cads developing a memory finally seems to have been abandoned).
Dry cells (alkaline are usually best) are most suitable where there are no facilities to recharge, such as when camping or on board a vessel that does not run its generator overnight. Most lamps designed to take dry cells will take the equivalent in rechargeable ni-cads (AA,C or D cells), so most can be converted to be "rechargeable".
If your well-being depends on your light working, at night for example, turn it on and leave it on during the dive. If you want to experience darkness, hold it against your body rather than turning it off. The current-surges during switching on and off put stress on the fragile element of the bulb.
Even we at Diver were surprised to find that as many as 76 different lamps were submitted for inclusion in this review.
These range from tiny penlights and mini-lamps that slip conveniently into BC pockets, to those similar in size to a domestic torch; powerful lanterns ranging from "pup" to "brute" and even "super-trouper"; and those light systems favoured by many technical divers that combine a large battery pack giving a long burn-time attached to the diver's tank or a separate belt with a lightweight lamphead fed by an umbilical lead.
Burn-times shown are from figures supplied by the distributors and are obviously affected by the wattage of the bulb employed. We asked distributors to supply working lamps fitted with bulbs of their choice and new or fully charged batteries.
Alas, some of the distributors proved less bright than their products, and there were a few hiccups to put right before testing. All torches were fully charged, or fitted with the appropriate alkaline batteries. We tested them in water over a set distance of 1.6m. We measured the width of the hot-spot of light, and its brightness.

Measuring outputMeasuring 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 in lamps 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.

SUPPLIERS
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.
Hydrotech 01455 274106.
Markat 01935 815424.
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.