Let there be lights! The road.cc 2021 Front Light Beam Comparison engine is live, helping you compare this year's lights

It’s that time of year again... the clocks have gone back, it's dark most of the time and here at road.cc we’re flipping the switch on the 2021 version of our front light beam comparison engine (hours of fun for all the family).

> The best front lights for cycling 2021/22

The light beam comparison engine

Our beam test comparison data contains beam shots and data for 36 of this year's lights, as well as all our historical data going back to 2015 – quite a lot of lights – so you can directly compare one with another. After it, we take a look at the various options in lighting technology and recommend some of our favourite lights.

If you have a nice big screen you can click here for the widescreen version (1400x1000px)

This year's lights – what have we learned?

We're still seeing the ongoing development of high-power LEDs, and for that reason bike lights are still getting brighter. There's been a bit of a hiatus over the past year, as a lot of light manufacturers have kept their lights the same, but even so the genral trend is towards brighter lights.

That being said, there's more variation going on in terms of beam shape. There are some SvTZO-compliant lights in there with German-style cut-off beams, but other manufacturers, especially Ravemen, Moon and Knog here, are using refractive lenses to shape the beam so less of it's going into the sky. The Ravemen lens, which uses two perpendicular sets of refractive elements to spread and lower the beam, is especially effective. 

We're still not seeing many light manunfacturers who do make SvTZO-compliant lights – Cateye and Lezyne, to name two – offer them in the UK, which is a shame as many people always comment asking for more choice in that part of the market. The choice is there: just not for us in the UK, it seems.

USB-C charging is becoming the default these days, especially for the brighter lights. It offers shorter charge times, and a double-sided design so you're not trying to jam it in the wrong way up. The contacts are a bit more widely spaced than Micro-USB too, which could be a benefit in the wet where it's possible to short out the port even if it's waterproof. A few manufacturers have been tweaking their brackets for a better user experience; more this year (including Moon and Magicshine) have moved to a Garmin-style quarter-turn mount which opens up a wide selection of after-market mounting options.

How we collect beam data

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 compare directly. 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, by taking a picture of each beam with the camera in the same position. Wider beams should appear wider, and if a beam isn't round you should be able to see what's going on with the shape.

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 was taken using the same settings on the camera: 28mm (effective 45mm), shooting for 1s at f29 on ISO6400, if you fancy doing some of your own. They're as directly comparable as they can be. If one looks brighter than another, that's because it was. Manny the Altura-coat-sporting dummy is at 10m (the cones are 2m apart) and the car is 20m away.

Although we use the same piece of road every year, it's very hard to make the beam shots directly comparable to other years. The road was wetter this year, and that means less reflected light from the surface compared to last year when it was drier, making the lights appear darker. So the only directly comparable shots are the ones taken in a single year.

A word about logs

The 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:

First, 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.

Second, 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.

And finally…

Bear in mind that having a very bright beam isn’t the whole story when it comes to deciding how good a bike light actually is. There are loads of other factors to take in to consideration when it comes to finding the best light for the cycling you do such as runtime, durability, ease of recharging; weather sealing; how good the clamping mechanism is etc, etc. It is a start though. We’ll be bringing you the full story on these lights in our upcoming reviews of them (some of them are already live on the site). Our road.cc light beam comparison engine will be living on the road.cc homepage throughout the winter. You’ll also find it on the Front light page of our reviews section too, and in the Front light buyers guide.