A widespread view is that all headlights within the same group of lighting technology are equally good. So all headlights with halogen lamps are the same, and that also applies to xenon technology and the latest ones with LEDs. Strictly speaking, that’s not true. There are a lot more criteria worth paying attention to. And quite a few are underrated.
- Homogeneity. What this means is that the light is distributed on the road as uniformly as possible. So there should be no big differences in brightness. Fanned out light distributions or dark areas are not just flaws; they also tire our eyes quicker when we’re driving at night. Such headlights have a restless effect, and identifying obstacles on the road is more difficult.Related to homogeneity is the width of the light distribution. Wider illumination on both sides – especially on the near side – is considered to be very pleasant. That requires a very high luminous flux. Halogen lamps can’t provide that. Once again, xenon headlights and many LED models are superior.
- As a rule of thumb we can say: the more luminous flux available in the headlight, the more homogeneous the light distribution can be. That’s the case with xenon. LED headlights with a single lens can also provide uniform illumination. But especially the first matrix systems had to deal with the chessboard effect. You could see the edges of the areas illuminated by the individual LEDs.
- Range. Actually, it’s logical that a headlight should illuminate the road as far ahead as possible. Strangely enough, most drivers don’t pay attention to the areas far away. The important ones are between 50 and 75 meters in front of the car on your side of the road. For this area to be as bright as possible, the headlights need to be adjusted very precisely. And the light source needs to accurately serve the optical system of the headlight. This requires very narrow tolerances during production. In lamps from Osram they lie within a range of hundredths of a millimeter.
- Glare-free high beam. Among lighting experts it is the innovation of recent decades. Visibility improves dramatically without dazzling oncoming traffic. The headlight always delivers as much light as possible. A camera detects oncoming cars and cars further ahead and only masks out the parts of the light distribution that is pointing at them. One level below glare-free high beam is adaptive light distribution. It’s mainly controlled by speed and adjusts the light to city, country road and highway traffic.
- Dynamic cornering lights are also among the underrated technologies. Here, the headlights follow the steering wheel angle. They illuminate bends a lot sooner than conventional types. Especially on country roads, dynamic cornering lights are a strong improvement. As a bonus, there’s reduced glare for oncoming drivers in near-side bends because the light moves away from them.
- The light source. The lamp is just as important as the headlight. Although they’re standardized, they’re not all the same. For example, the H7 halogen lamp which is considered very powerful should provide a luminous flux of 1,500 lumens according to regulations. For this parameter alone, some no-name products produced test values less than 1,000 lumens. There were also geometrical faults, in other words the exact position of the filament. The problem is that even the trained eyes of experts don’t see most faults. And who of us has a measuring device for luminous flux? With brand manufacturers such as Osram it’s a sure thing that lamps will not only exceed the legal requirements, but exceed them by a significant margin.