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Appeared in DIVER February 2008
Thirty back-up lights, switched on and ready to shine, but which one would you want to find in your BC the day everything goes dark? John Bantin and Colin Mac Andrias put them to the test
One diver's back-up light is another's primary diving light, if some of the suppliers we approached for this comparison test are to be believed.
Our intention in putting together this review was to look at the sort of lamp you could carry stowed in a pocket or mounted on a BC on every dive. Should that awful moment come when you are unexpectedly left in the dark, you can then find it easily, switch it on and read your instruments as you head back out of the wreck or up to the surface - and still be found by your pick-up boat if it's a night dive.
Of course, it would be nice if you could see where you're going, too!
Some people would argue that a redundant diving light should be as good as a primary and that you should always treat your back-up light in the same way as that primary. You should check its operation immediately before diving, and maintain it scrupulously between dives.
Yet many of us stick back-up lights in our pockets and forget them until we need them.
In our test you can see the shape of each beam as it was photographed. Bear in mind that these images do not indicate brightness.
Brightness is not about how much light is produced at the lamp, but about how much light arrives at the object at which you point.
This depends on the efficiency of the lamp's reflector, so don't be misled by manufacturers' claims.
We give a factor for brightness measured at the end of each beam, shone over 2m. This reveals the number of times brighter each lamp is than the dimmest we tested.
The most important aspect of a back-up light is not how bright it is or the shape of its beam, it is that it works reliably. Many manufacturers unfortunately resort to using the simple screw-down shroud as a switch.
This makes the manufacturing of a watertight product more foolproof, but does not make the light proof against foolish use of it.
Reliability is the one aspect at which we can only guess. The time it takes to test a product for long-term reliability would be more than the commercial life-span of many products, so you will have to put up with educated guesses based on our combined experience.
When Colin managed a busy dive centre, those who rented torches were told to have them turned on before they entered the water and not to turn them off until they were safely out again. He found that he could not trust most divers not to fiddle with them and accidentally flood them.