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We measure light output in our lab. Many lights make output claims in lumens, which describe the total amount of light available. However, we think lux (lumens per square metre) is a better measure of light performance. We measure lux at 0°, 20° and 45° to build up a picture of the quantity and quality of light output.
For front lights we calculate light performance combining 40% of the score at 45°, 40% at 20° and 20% at 0°.
For rear lights we calculate light performance combining 20% of the score at 45°, 40% at 20°and 40% at 0°.
This includes an assessment of “in-use” performance (50% of the ease of use score), which includes turning the light on and off and selecting the mode (with and without gloves), usefulness of the battery indicator, and robustness of the mount to knocks and vibration. Daily convenience (30%) includes removing and refitting the light, charging or changing batteries and carrying it in a bag. Ease of fitting and versatility of the mount adds the final 20%.
We left the lights outside for several hours during heavy rain, then thoroughly doused them with a garden sprinkler for a further 2 minutes. We checked they all worked correctly while soaking wet, then towel-dried them and inspected for any water inside the lens and battery compartment or charge port. We don’t include water resistance in our overall score, but we won’t recommend lights that show signs of water ingress.
We measured burn time of the USB rechargeable lights on their maximum steady setting. If they switched to low-power mode as the battery drained, we recorded the time spent on full and low power.