Let there be lights!
High-intensity headlight bulb test
Even though there are different headlamps available for a given car, the easiest way to improve the lighting power of the headlamp is fitting a premium, high intensity filament bulb.
We are getting older and our eyesight is much less sensitive than it was when we were younger, or we just have to drive a lot at night times – in both cases the best way to improve visibility is fitting a bulb with the same wattage but higher intensity.
The H4 bulb, one of the last dinosaurs of its kind, is still used by many. This was the most popular filament bulb in the past, today however the newer H7 format starts to replace it. The H7 has one filament, the H4 has two filaments so it has the reflector and the dimmed beam fitted in one bulb.
Since the law only prescribes the shape and wattage of the filament bulb, you can get a higher light intensity from a H4 bulb and still be within the standards, so the auhorities will still accept it as officially legal. The higher wattage – 80/100 W – bulbs are illegal, so it is also illegal to mark them as H4 standard on the package. .
According to our plans this test will consist of two phases. In the first phase we are going to make laboratory measurements in the meeting room of Totalcar, while the second phase will consist of a real life test, so we are going to fit the bulbs into our normal cars used everday. Unfortunately my own Beetle, the old Merc of a colleague and the Autobianchi Bianchina of another are not going to take part in the show, since they are using older R2 non-halogen filament bulbs.
In the real test we will check whether the light intensity decreases after the bulbs are fitted into the cars and we will check wheter their lifetime is longer or shorter than that of the regular bulbs. It is common knowledge that the brighter ones have a shorter life cycle.
All the tests are repeatable and all the circumstances are defined properly. The repeatability almost failed when I made a wrong move and all the test equipment almost fell down and crashed. It was close call, but no harm was done.
The laboratory was chosen to be the meeting room of Totalcar since it has only one window and is easy to make a dark room of it. Also it is at least 4 meters long, so we do not have to project the light on the white wall from a mere half meter. We fetched a photo lightmeter (serial number, type and make in the office) and made the test equipment out of a cupboard box and a Golf I headlamp made by Bosch in 1977. This headlamp is a parabolic type, and it's quite easy to change the bulb in it, moreover the position of the bulb is pretty much the same after each change. This is very important, since the beam pattern projected on the wall actually depends on the position of the bulb.
The power supply was a 55 Ah battery and an automatic battery charger, so the voltage was absolutely the same at each measurement. The changer can supply up to 8A but we need only 2-3 amps since the battery was in very good condition, just taken out of my car.
The voltage has a very important role: higher voltage means higher illumination up to a point where the life cycle of the filament ends. The voltage was exactly 12.7 V at each measurements.
The bulb has other important factors other than light intensity. The size, the geometry also play a very important role, because the bulb is the starting point of a nice and even beam pattern. The second step in the way of the light is the lamp itself, the size, the mirror and the glass of it, since it determines the beam pattern. In that case it was a rather old type of lamp. If the bulb is out of specification regarding the size and position of the filament, then the beam pattern will be awful, and at the end the visibility and the light intensitywill decrease. The best way to to measure the size and the geometry of the bulb is to do it indirectly, by measuring the light intensity outside the euro beam pattern. As a bulb gets more and more out of the specification, the more light will appear outside the beam pattern, that is for sure.