08 Nov 2012

When it comes to the lumen output for LED lights, mountain bikers are like rabbits caught in the headlights – hypnotised by manufacturers’ claims about brighter light for less money.

Halogen globes, lead acid batteries and watts are terms that are all but extinct in today’s bike light market. Out on the singletrack we have entered the world of LED lights and lithium ion batteries, and when we want to compare light output now, we talk about lumens. [private]

Getting all luminary

The lumen has become the buzzword in the headlight market.

Most of us drool when we read that the lumen output on our most coveted model of headlight will double from one season to the next. But how many riders actually know what a lumen is? How it the measurement taken? Is it accurate? And is it really the only thing to consider when shopping for LED lights?

The lumen is a measurement of the amount of light contained in a certain area, as compared to a watt, which is a measurement of how much power is required to run a light. In theory, measuring the amount of light contained in a certain area should be more pertinent to lighting in mountain biking, where the key application is lighting up that singletrack at night.

Unfortunately this may not be true.

Many light companies claim their lights have a certain lumen output, but where do their stats come from?

Measuring lumen output accurately is a complex exercise and requires the use of an expensive piece of equipment called an integrating sphere. But don’t assume that all manufacturers get their light output stats this way. Some manufacturers use light meters, and some quote the lumen output from the LED manufacturer. These methods are not as accurate.

It’s not all about the Lumens

Falling in with the wrong crowd

Head units comprise more than just LEDs. They also contain lenses and reflectors, and these, together with the LEDs, will determine how good your LEDs are. You could have a headlight with the brightest LED ever, but if its lenses and reflectors are low quality and poorly designed, that headlight’s beam spread won’t cut it on a night ride.

Beam spread is critically important. There is no point having the most powerful LED if all it does is light up an area the size of 50-cent piece. LED lights need a strong bright spot and an even, wider beam to give you a nice balance of light out on the trail.

Heat is also a major enemy of the LED. (Think Superman and Kryptonite.) Heat can affect a light’s performance and running-time dramatically. So keep this in mind when comparing cheaper lights that claim to have the same lumen output as higher-quality units.

Good quality lights will include a heat sink in their design, to disperse the heat away from the light’s head unit (usually a nicely CNC-machined fins). By maintaining a cool operating temperature, the heat sink allows the light to run as close as possible to its claimed lumen output.

Cheaper lights don’t stand a chance of reaching, much less maintaining, their claimed lumen output once they are out of the box. El cheapo, poorly designed head units warm up all too quickly when in use on the trail, and they will overheat as soon as you stop for a mid-ride chat.

There is more to choosing your next light that the big numbers companies throw at you. Look a little deeper and see what else they have to help you see the path ahead of you better (and for longer).

A good hard look

Most riders think brighter is better, but where will it stop? There are manufacturers out there spruiking lights with over 3000 lumens – but do we really need that much light?

No matter how many lumens a light unit can produce, riding at night is always going to be riding at night. Light manufacturers will never be able to turn night into day.

In some situations lights cause bad glare, by bouncing off heavily populated forest areas. Your lights can also cause glare on cool damp winter nights, when the beam bounces off fog and mist as you wind your way around your favourite singletrack.

Let there be light

When searching for your next LED light set, consider more than just the price and the claimed lumen output.

Use the lumen output as a rough guide – remember most manufacturers can’t accurately measure lumen output, and even if they could, lumen output is one of many factors to take into account when looking at LED lights.

Beam spread and the functionality and reliability of the head unit are all important. Also consider the quality of the brackets that mount the head unit to your handlebars or helmet, the running time of the battery and the size of the light set as a whole.

Take your time. Work out what you need from a LED light set, and don’t be lured in by the lumen!

Some lights are there just for fun but on the trail you need more than a cheap toy to keep you safe.