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Light distribution

Here you will find useful information and handy tips relating to light distribution for low beam, high beam, and country lights.

Every driver knows the light functions "low beam" and "high beam". Modern lighting systems also provide additional light distribution options, gaining the best illumination of the road whilst taking into account the legal specifications. Here you can read about the tricks used to realise this, and what the deal is with new lighting functions, such as country lights.

Important safety note
The following technical information and practical tips have been compiled by HELLA in order to provide professional support to vehicle garages in their day-to-day work. The information provided on this website is intended for use by suitably qualified personnel only.

 

LIGHT DISTRIBUTION FOR LOW BEAM LIGHTS: COMPARISON

The low beam is an important component of the vehicle lighting and is a statutory requirement for every vehicle. The essential purpose of the low beam is to provide safe lighting of the roadway at close range in front of the vehicle without dazzling other road users. Special requirements therefore exist in relation to the luminous intensity and light distribution, which is generally asymmetrical. The low beam also ensures that the vehicle is also easily visible to other road users in the dark.

Halogen headlamp, low beam

For halogen headlamps the light distribution in the area of the asymmetrical light component demonstrates a clear 15° increase. This has been and also remains the most widespread light distribution to date. The continuous increase of the asymmetrical component is also typical of this characteristic. The light colour is whitish yellow due to the halogen bulb.

 

In the adjacent graphic, which illustrates the light distribution, the symmetrical light component to the left of the vertical "zero line" (oncoming traffic) runs just below the dashed "cut-off line". This means that oncoming traffic will not be dazzled. For increased visibility on the driver's lane and the right-hand edge of the road, the asymmetrical light distribution increases the range.

Bi-Xenon headlight, low beam

For the low beam light distribution of Bi-Xenon headlights a more shallow increase (12°) in the asymmetrical light component can be seen. The increase is between 12° and 75° for an increasing number of headlamps. The asymmetrical light component shows a "kink" in its shape. This does not represent a fault in the headlamp, however. This characteristic is necessary to ensure that the requirements for specific lux values in the light distribution in accordance with the corresponding ECE regulations are not exceeded due to the high light intensity. Due to the xenon system and associated higher Kelvin value, the light colour is whitish blue.

 

To the left of the vertical "zero line" (oncoming traffic), the symmetrical light component runs just below the dashed "cut-off line" for the light distribution graphic shown. This means that oncoming traffic will not be dazzled. The asymmetrical light distribution increases the visibility of the driver's own lane and the edge of the road.

LED headlamp, low beam

In the LED low beam light distribution, the increase in the asymmetrical light component is similar to the previous Bi-Xenon system. The asymmetrical light component demonstrates a "kink" in its shape (see arrow). This does not represent a fault in the headlamp, however. The purpose of the increase is to identify black and white guide posts or the centre line marking more easily and sooner.

 

In the graphic, the symmetrical light component to the left of the vertical "zero line" (oncoming traffic) runs just below the dashed "cut-off line". This means that oncoming traffic will not be dazzled. However, a small asymmetrical increase in the light distribution can be clearly seen on the left-hand side.

LIGHT DISTRIBUTION FOR HIGH BEAM AND COUNTRY LIGHTS: COMPARISON

In addition to low beam, high beam lights are also a mandatory part of the vehicle lighting. In contrast to the low beam, the high beam illuminates the road to the maximum possible extent. The high beam is therefore predominantly used on very dark sections of road without oncoming traffic where it is difficult to see what lies ahead, thus significantly increasing visibility and therefore safety on these roads, also during faster journeys. In addition, the high beam is used to operate the headlamp flasher.

Classic high beam

The high beam distribution which can be seen on the photos/aiming screens clearly shows the differences between the classic high beam and the high beam of an LED headlamp. The classic high beam describes a rather more spot-based or oval illumination around the centre mark (small square).

LED headlamp, high beam

With the high beam of an LED headlamp, a much greater area is illuminated. Although in this case the greatest light intensity is also around the centre mark, the light can be distributed over a wider area due to the greater "light output" of the headlamp, however.

LED headlamp, country light

This light distribution is only activated once a specific speed has been reached. Depending on the manufacturer, this is between 50 and 80 km/h.

 

Raising the cut-off line (shown in the graphic) in the area on the left improves the illumination of the road and side areas. The asymmetrical light component is steeper at 60° and the "kink" can be seen much earlier.