Car headlight bulbs explained
Our tests
We have compared the so-called ‘brighter’ halogen headlight bulbs with standard-fit items (in two Vauxhall Astra test cars), and also with xenon headlights. In the tests we carried out, we used the best-selling ‘H7’ size of bulb and compared bulbs sold by Halfords and Bosch with the original-equipment bulbs in the Astra, alongside an Astra with a xenon headlight upgrade (costing £766 at the time).
We aligned the lights at a fixed point on an unlit country lane, and took lux (light-level) readings at 10, 25, 50, 75 and 100m in front of the car. Two readings were taken at ground level, one facing upwards and the other facing the car, and one reading was taken at 1m high (pedestrian level). We also tested them at dipped beam and main beam. Photographs were taken from the driver’s seat to give a subjective assessment of light brightness, spread and colour.
The xenon bulbs quite literally outshone all the halogen bulbs in our test at 10m and 25m, scoring five stars for both dipped beam and main beam performance. They were particularly strong at main beam.
However, we found that xenon light did tend to cut off quite sharply at greater distances, with no light reading at all on dipped beam at 75m. Most of the halogen bulbs we tested managed one or two lux.