FOR YEARS, UNDERWATER LIGHTS WERE SIMPLE to write about. They had a bulb, the brightness of which could be determined simply by checking the wattage, and they had a battery that could or could not be recharged.
Super-bright halogen lamps offered extra performance but came with the drawback of bulky high amp/hour batteries to power them. Then everything changed.
First LEDs came onto the market, usually mounted in clusters. These by and large were a dismal failure because, although they looked bright, nobody had worked out a way of getting the light projected forward in a usable beam.
Then some bright spark had the idea of mounting an HID light, developed for bright reliable lighting in operating theatres, in a lamp for diving. The output was phenomenal.
Alas, divers tended to be a lot clumsier than eye surgeons, and breakages occurred.
It was at this point that the reality of the replacement cost of HID bulbs struck home. Since then things have improved, with the HID bulbs now used in some hi-tech modern cars being employed instead.
The rigours of high-speed motorway cruising are more akin to the diving environment than the sterile and, one hopes, peaceful conditions of the operating theatre.
Just as we equipment reviewers were getting a handle on this, super-bright LEDs were developed. At first these were employed in smaller lights of the type usually kept for back-up and, because they produced a lot of light from a single-point source, they worked well in conventional lamp reflectors and shone a useful beam.
What immediately became apparent once these lamps started getting used by divers was that they were incredibly robust.
A modern LED produces a lot of light for very little power consumed, resulting in very long burntimes unheard of 20 years ago. It also seems to withstand a lot of rough and tumble - just what you need with rough divers tumbling on top of diving equipment in the unstable circumstances found in small boats at sea.
Manufacturers started looking at how to get increased light from these super-bright LEDS, so that they could incorporate them into primary diving lamps. Simply clustering them together was not going to work. Successful lamp design depends on the reflector and, while designing a parabolic reflector that pushes all the light emitted forward might be simple for a single-point source, how could it be done with multiple LEDs
It couldnt. The solution was to include an individual reflector with each and every light source, and today we see higher-output LED lamps with several smaller lamps mounted behind a single front glass.
Green Force, the Belgian manufacturer, came into the underwater lighting business at exactly the right time. It has been able to keep pace with all these developments easily, because of the modular design of its original lamp.
It used a battery-pack that I described unkindly as very old-fashioned when I first saw it. A separate lamp-head could be screwed into it. By fixing a handle this becomes a hand-lamp, or by fixing a cable with male and female screw-in connectors, it can be an umbilical lamp.
This gave Green Force the strategy of changing the components, including both battery and light-source, and offering new and updated versions.

Light Source
Electronics advance at such a pace today that it is hard to write definitively about anything. Just as we got used to the high output of the three-LED TriStar 15 head that Green Force offered, it brought out the TriStar Max, offering more light for less current consumed.
The best way to describe it is as giving a light equivalent to that of a 55W lamp in an old-fashioned tungsten style of 55W as opposed to, say, the 50W of its predecessor.
You could also say that The old lamp had a brightness that went to 10 whereas this one goes to 11 but that would be blatant plagiarism from Spinal Tap.
Its a little smaller, too, and weighs around half a kilo out of the water. It has three of the latest high-output LEDs, and they appear to be enclosed in resin that includes both the reflector and a lens.
Even if I am deceived by appearances, and there is an air space behind the front glass, the LEDs each include a lens, and the reflector is designed very accurately to make sure all the light produced goes where you want it.
Im told that each LED has its own electronics, so should one fail the others will continue to work. This can provide a secure feeling to those who dive in very dark places.
The head is made from marine-grade anodised aluminium with a heavy-duty front shroud of a rubber compound. The overall effect is that of a very high-quality item.

Power Source
Green Force now offers a variety of power sources, but lets assume that you pair the TriStar Max with the standard F2 ni-mh battery pack. Its 12V, 4.5amp/hr unit is housed in a permanently sealed Delrin container. This is ribbed to give it a good grip, whether you want to hand-hold it like a torch, or strap it to your tank and use an umbilical.
Nickel-metal hydride batteries can be recharged safely at any state of charge, without damaging the battery or causing it to suffer a charge memory-effect.
So you can keep it topped up and always ready to deliver the full nine yards of burntime, using the intelligent charger supplied with it. It can be recharged from its lowest state in just over three hours.
A pressure-relief valve protects against the build-up of battery gas. The LED head actually consumes only 15W, so a burntime for a fully charged F2 unit is more than three hours.

This has always been a problem area for me. The Green Force lamps universally use a simple system by which you screw the lamp (or lead end) into the battery so that it bears down to make a contact. Its the way a lot of cheap and not-so-cheap back-up lamps do it.
The Green Force components are protected by three O-rings in line, but among a lot of divers I have met, unscrewing a lamphead just enough to switch it off can be problematic.
Its a question of never forgetting that old rule righty tighty, lefty loosey.
I have witnessed otherwise intelligent people under water unscrewing the head of their lamp until it floods in an effort to switch it on. Nitrogen narcosis or lack of finesse
Switch it on before entering the water and dont turn it off until youre back out.
The other point is that if you use this head in conjunction with an umbilical cable, you have two points at which it can be switched on and off. Ive seen that lead to confusion under water, too.

This optional extra comes as a length of almost 1m, and has the male and female connectors equipped with the three protecting O-rings.
The outer layer of the cable is a waterproof pressure hose, and the electrical cable runs within it so that water and electricity are kept well apart.

Its difficult to make objective judgements about brightness without comparing with another lamp, because our eyes have such a wonderful ability to adjust to any level.
The TriStar Max is obviously very bright, as the maker claims. I set it up in our standard underwater lamp-test rig and took a photograph so that you can compare the quality and shape of the beam, if not the brightness, with lamps we have compared in our most recent group tests. The beam was very even, considering that the light was from three separate sources.
While it was obviously brightest at the middle, it faded off very gently, giving a huge area of peripheral vision with no hint of any colour-fringing caused by chromatic aberrations in the little lenses of the three LEDs.
Thanks to the strength of the euro, you might now pay top dollar for a Green Force lamp like this, but it is a hard product to fault.

Diverite LT6079 LED 500, £420
Salvo 12W Rebel LED, £480
Fa & Mi MultiStar 50 LED, £378

PRICE £520 with F2 battery-pack
BATTERIES F2 ni-mh rechargeable
EXTRAS See on-line catalogue
WEIGHT 400g (head alone)
DEPTH-RATING 300m (Delrin parts) 500m (aluminium parts)
DIVER GUIDE width=100% width=100% width=100% width=100% width=100% width=100% width=100% width=100% width=100% width=100%