About the beam comparison engine of bike lights

We've collected lots of beam data so you can compare and contrast the different lights. Light manufacturers use a number of different metrics to describe light output. We've used lux here, but measured at a number of points across the width of the beam. That gives an indication of the brightness of the beam at the centre, the amount of peripheral light and the throw of the beam. We think that's the most useful measurement to directly compare. Specifically, we measured the lux value of the beam at two metres distance, in 10cm increments from the centre of the beam to 1m from the centre, giving eleven readings.

We've also included data on the shape of the beam. In previous years we've struggled to get a meaningful shape for many lights using a fixed position, so this year we've been a bit more subjective. The lights were positioned such that the shape of the beam was most noticeable, then readings taken from 0° round to 180° in 30° increments. Then the numbers were normalised for all lights, to a maximum value of 10. That gives an indication of the beam shape.

Most of the lights we tested still had a more-or-less round beam. For riding on the road a squared-off beam has advantages. You're not wasting your battery lighting up the tree canopy, and you're less likely to dazzle oncoming traffic. Such beams are widely used in Europe, and in Germany they're the only lights legal for use on the road.

To get a good idea of what each beam looks like, we set up a bike on a rig so that we could photograph the beams of all the different lights in a comparable way. Each of the beam shots you can see above was taken using the same settings on the camera: 28mm (effective 45mm), shooting for 2s at f22 on ISO3200. If you fancy doing some of your own. So as much as they can be, they're directly comparable to one another. If one looks brighter than another, that's because it was. Skardy the Altura-Night-Vision-sporting model is at 10m (the cones are 2m apart) and the car is 20m away.

A word about logsThe graph displaying the beam data uses a logarithmic scale to display the output of the lights. If you understand or care about such things, here's why:

Firstly, light beams follow an inverse square law regarding the strength of the light at increasing distance, because they're illuminating a two-dimensional plane. So at twice the distance, the light beam is spread over four times the area. Consequently, a light that is measured as twice as bright at its centre won't let you see twice as far. The logarithmic scale produces a more realistic visual comparison because of this.

Secondly, the variations in the amount of peripheral light, though much smaller than the variations in the centre, make a big difference to how much peripheral vision you get. The logarithmic scale amplifies these differences relative to the centre of the beam, so it's easier to see which unit is putting out more light at the sides.

Recommended lights：Spiker 1210 mtb Floodlight - US135.00D2D Elite - US279.00D2D Entrant - US269.00 Panasonic 6 - US125.00 Spiker 1206 Handlebar/ Helmet Light - US119.00