HEADLIGHTS: BEAM PATTERN

DIP BEAM...
...the most important lightunits on your car! Because this is the light you will use most of the time. All the full beams in the world will be of no help to you, when oncoming traffic forces you to switch them off. A dip beam unit is supposed to distribute the light evenly on the road, aproxomately 60 metres ahead, or more. This sounds easy enough, but in reality its far from it. One "problem" is that light is reduced by the square of the distance. In plain english, this means that: If we measure the output of a lightunit to be 200 lux at 5 metres, it will not be 100 lux at 10 metres. It will be 50 lux ! At 20 metres? …12,5 lux. And at 40 metres it will be 3,25 lux. So, in order to get an evenly light pattern in front of the car, we need to direct four times as much of the available light, to where it will hit 50 metres, than to where it reaches 25 metres. If you park the car at night with the nose five metres from a wall, and switch on the dip beams, you'll see the beam pattern of each unit projected on the wall. You should now be able to draw a horisontal line from left to the center of each pattern image. From the center, and to the right, the line shoult tilt upwards fifteen degrees. (this is why dip beams illuminate the right shoulder further ahead) Above this line, there should be no light. This imaginative line is reffered to as the light/darkness boarderline. Below this line, the light should be strong, and gradually decrease further down. (For our friends in the UK, and other RHD countries, the light pattern is of course reversed)

FOG LIGHT
The purpuse of a foglight is to illuminate the near-field in front of the car, during reduced visibility conditions. It should have a very sharp light/darkness boarderline = NO WASTELIGHT! It's pattern is supposed to be very wide, and is ideal for curved B-roads, where it "beams around the curve".

They are a very useful supplement, if the units are good. On many of today's cars, this is not often the case. Tiny, front spoiler mounted, quirky shaped original foglights scaresly manage to illuminate the first three metres in front of the car. (the area you cant see) It seems the phrase "near-field" has been taken a little too litterally. And many of them have so much wastelight that they are a constant nuesence to oncoming traffic. A lot of new cars have them, purely for cosmetic reasons.

On the other hand, there are some good original foglights out there, and most aftermarked units are ok. The best original foglights I've seen, are the ones on Mercedes W 123. On their next model (W 124) the foglights were still good, but not the best. On their next (and current) model (W 210), the foglights are downright mediocre. There's progression for you.

W123 (76-86)	W124 (85-95)	W210 (95---)

FULL BEAM
The mission of a full beam is quite simple: To cast as much light forward as possible.
But: Not too much near the car, it'll ruin your night-vision.
And: Not too much upwards, we only have so much light, we need to direct it where we can use it. Preferrably on the road from 70 metres ahead, and onwards. And can we have some light to the sides too, please? We'd like to see the elk before it jumps out in front of us. (Ooops, it seems the mission wasn't so simple, afterall?)

AUX. DRIVING LIGHT
Actually a full beam unit, only larger and more powerful. With some exeptions, but this article is not about them, we'll concentrate on the large ones. There is no substitute for sheer size, and round lights are always better then rectangular ones. Most aux. driving lights come in two versions: Normal (flood), and pencilbeam (spot). The "pencilbeam" has, as the name indicates, a long thin beam of light, nothing is distributed to the sides. Ideal for high-speed cruises on straight lonely motorways. Useless for anything else.

Some people overdo it.	Some people reeealy overdo it.

Saab 99, dip	Saab 99, full	My 99, dip	My 99, full	The WALL

98-Mondeo, fog	98-Mondeo, dip	98-Mondeo, full	98-Mondeo	.

It must be noted that photographing light is a near impossible task. A fully automatic camera will compensate for differences in light-intensity between units, and therefore NOT give a true picture.
But we CAN get a usable image of the pattern.