Torch Technology and what it all means
It seems nowadays that everywhere you look there’s a new torch or video light for sale, all boasting amazing high power outputs, see for miles, burns for hours and hours… well I thought I’d throw some light (forgive me the awful pun) on the subject and try and clarify all the jargon and gobbledygook.
Lights on the surface seem to be very simplistic bits of equipment; some batteries, a bulb, some wiring and a case to fit it all in, and there you go – you’ve got a torch. Unfortunately a great many of the torches and lights available at the moment are exactly this, and the technology behind LED lights is a great deal more complex than that. Let’s work through some of the basics which hopefully will make choosing your next light easier.
The one term that gets bandied about left, right and centre is lumens. It would seem that lumens are the brightness of a light source… well, yeah, kinda, but it’s not quite right. A lumen is a very specific measurement of light emanating from a single point and measured equally on a surface a given distance away from that point, surrounding it on all sides, normally a sphere. Because of the vast amount of exaggerated claims by torch manufacturers in the US they have come up with a specific standard for measuring the output of torches, which is called ANSI/NEMA FL-1. This is very expensive to do because of the cost of the testing, so only the more dedicated manufacturers have their products certified. Look out for this on product packaging to be sure of a quality bit of kit. A small light will output 500 or 600 lumens nowadays with the top end kit producing 4000/5000 lumens, which is incredibly bright indeed. Some of these torches cannot even be turned on for more than a few seconds out of the water as they will start to melt without the water to cool them. These powerful lights even have safety mechanisms to prevent them from being switched on accidentally and this is now a legal requirement if you want to take them on a plane. When using these lights, even the less powerful ones, be mindful of not pointing it at other people as it is quite unpleasant being blinded by one of them – especially on a dive.
Another thing to be very mindful of is the fact that a very large number of LED torches on the market will, when turned on initially, achieve the quoted light output, but very quickly (sometimes within seconds) dim down to only a fraction of what they are meant to achieve. The better quality lights will maintain their output with just a drop off of about 10% all the way through until the battery is depleted. The Light and Motion range along with the exotic Keldan and surprisingly the Ikelite lights all perform very well in this respect. Newcomer RGBlue is also very well designed and works well throughout the battery life.
Talking from a video point of view a classic failing of inferior lights is the edge definition. We see many torches advertised as video lights and within seconds of turning them on we soon realise they’re just another torch. Video lights have a very specific quality and that is that there is no hard edge to the beam; instead the output bleeds off very gently. If they don’t do this the camera sees the edge and it stands out very clearly and looks poor. On this point something else worth mentioning is the beam angle. Many lights quote how wide the beam is for the benefit of the videographer. What is not considered is the fact that as soon as you take most torches underwater the beam angle is significantly reduced. To my knowledge there is only one light on the market which addresses this issue and that is the UK Aqualite Video 90. The Video 90 cleverly has a small dome on top of the emitter which corrects the refraction and the beam width remains exactly the same in and out of the water. Another thing to be mindful of is that good LED lights have a ‘controller’ that regulates the output, maintaining the power. On some cheaper lights this can cause a slight flickering, which is not always visible to the naked eye but unfortunately very visible to the camera eye.
More serious videographers will also be concerned over the colour temperature of a light. We don’t notice it so much but all light has different colour properties. It’s quite an in depth subject and I don’t want to make this article too technical so I’ll keep it brief. White light is a mixture of all visible wavelengths of light. Different wavelengths represent different colours so in essence white light is a mixture of different colours. Depending on the manufacture of an LED emitter and the design of any light or torch, which may have a mixture of different emitters, the light will have a caste or slight bias towards a colour. A shift towards blue, for example, will make video or stills appear cooler. A shift towards red gives a warmer feel. Purist photographers/videographers will prefer a light which most closely simulates daylight. Colour temperature is measured in degrees Kelvin and daylight is measured at 5500° so look out for this on the box (although that is no guarantee that it will deliver that but it should be closer than if it doesn’t say anything at all).
From a photo/videographic point of view it is worth researching the right light before you buy otherwise you could be throwing money down the drain, and let’s face it – these things aren’t cheap.
