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There are several unalterable truths about diving that make the purchase of a
dive light an excellent idea: (1) If you’re diving at night, you won’t be
able to see anything without a light. (2) Even during a daytime dive, a light
is useful for peeking into cracks and crevices. (3) A candle in a baggie
simply won’t do the trick.
Time of Use
Your first decision should be to examine when you’ll be using the light. If
you’ll be using it primarily at night, you need to think about overcoming
total (or near total) darkness, which probably means a light with a
sufficiently wide beam and high luminosity. For daytime diving, the need for
illumination is limited to peering under ledges, holes, wrecks, etc., which
means you can use a light with a much narrower beam angle, and without as
much candlepower.
Beam of Beam
This simply refers to how large an area the light covers. But there’s a
trade-off between beam width, brightness of the light, and power
requirements. The wider the beam, the less bright it will be, unless you
increase the power (and usually the price) of the light. A narrower beam will
be brighter but cover less area. So unless you want to dive with a couple of
car batteries strapped to your back, you’ll need to decide if “wider” or
“brighter” is more important to you.
Brightness
One way the manufacturers have dealt with this is to create lights that have
two beam areas. The primary area is the bright spot in the center of the
overall beam, while the secondary area is a much dimmer (and wider) area
outside of the central primary area. By constructing a light this way, you
can get the advantage of brightness and width without having to tremendously
increase power.
Testing for Width
For the easiest way to see how wide and bright a beam is, go to your local
dive shop and shine the lights against a wall. This is also a great technique
for comparing two lights, as you can shine them side by side. But it’s
important to remember that in the water you won’t really be using your light
for objects greater than five to 10 feet away, so that’s how far you should
stand from the wall when you’re testing a light. This will make the beam
width and intensity similar to what you’ll see underwater.
Candlepower Isn’t Everything
An initial impression might be that you want the brightest light on the
market. But that’s not always the case. If you dive in water that’s
especially turbid or has a lot of suspended particles, a brighter light may
actually hamper your visibility, since it makes particles more visible.
However, if you’ll be diving in water that’s generally clear, a brighter
light with wider beam will allow you to see more stuff.
If you’re a photographer shooting at night and using a dive light as a
spotting light, you may also want to think about something slightly less
bright. Extremely bright lights can spook the fish you’re trying to shoot or
possibly mar your image by leaving a hot spot in the center.
Size and Weight
Dive lights best suited for nighttime diving will generally be larger than
their daytime cousins, which can usually be slipped inside a BC pocket. But
since you’ll be keeping the light on all the time and using it throughout the
night dive, size is not a major issue (the assumption being you’re holding it
in your hand).
A daytime light, since it doesn’t need the candlepower to light up the
evening reef, will be relatively small and compact. It should fit comfortably
in your hand with the on/off switch readily accessible. And since you’ll
probably use it only intermittently during the dive, you want it to fit
comfortably inside your BC pocket.
Batteries vs. Rechargeable
The advantage of batteries is that they last a relatively long time. But
since you use up some of the charge each time you turn on the light, the
strength of the batteries diminishes over time. This means your light will be
growing ever-so-imperceptibly dimmer. But all it takes is a fresh set of
batteries to restore the light to its original intensity.
Rechargeable batteries will give you a more consistent level of light output,
but when they start to go, they go pretty fast. And while it’s unusual for a
battery-powered light to die during the dive (unless you just unearthed some
16th century doubloons, you’d have noticed it was getting dim and changed the
batteries before they were fully drained), it’s not unusual for a
rechargeable light to wink out on you towards the end of your dive. However,
when it is time for a recharge, all you have to do is plug the light in for
the recharging period, which can be anywhere from a few hours to overnight.
If you’ll only be using the light for one dive a day, a rechargeable can be a
great way to go (though they are a bit more expensive). If you’ll be using
the light a lot without much down time, you might want to stick to batteries.
In fact, many divers use a battery light in the daytime and a
rechargeable for night diving (the daytime light also makes a great nighttime
backup).
Lanyards
While most lights come with a lanyard, if the light you’re looking at doesn’t
come with one, buy one. It’s cheap insurance against losing the light.
Specialty Lights
A couple of manufacturers make dive lights (mostly for nighttime or cave use)
that fit on your head or mask strap. These are especially useful if you want
to have your hands free, as the light will always be pointing in the
direction you’re looking. Just remember not to look your dive partner in the
eyes or you’ll have one blind-ass buddy on your hands.
Other Goodies
Once you have a light, it’s always good to carry an extra bulb, a spare
lanyard and extra batteries with you. With some of the bigger lights, you may
have the option of switching between a pistol grip and a lantern grip.
There’s a world of wonder that lurks in the shadows of the reef. Seek the light,
slip into the water and see what you’ve been missing.
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