Yep - agreed. The biggest problem is definitely where the light source (especially a significantly brighter one) originates from a different position relative to the reflector. Then it is obvious that the light will be reflected in a different pattern.
Most of the better quality HID globes these days however, have addressed this. In the case of a H4 replacement, the HID light source "arc" is as near as dammit to the position of the filaments in a standard halogen H4 globe.
In the case of the hi/lo beam halogen globes, there are actually two light sources (filaments). The low beam filament sits above a "shutter" which prevents light from the filament reflecting onto the bottom half of the headlight reflector. The bulk of the light from this source (filament) is directed toward the top half of the headlight reflector, and from there is reflected downwards - producing low beam light pattern. The high beam filament sits clear of this "shutter" and when illuminated, light emitting from the hi beam filament can pass to the entire diameter of the headlight's reflector, thereby producing hi beam light pattern.
The HID globes that I have in the Disco have a single light source or "arc". The way that hi and low beam patterns are achieved is that the HID globe moves in or out in the headlight housing to position the light source either above the "shutter" which directs the light to the upper half of the headlight reflector (lo beam) or clear of the shutter so that the light can pass to the entire diameter of the headlight reflector (hi beam). The "shutter" is external to the HID globe and remains stationary. I have checked, and the positions of the light source when in both the hi and lo beam are exactly the same as in the case of a standard H4 halogen globe, relative both to the headlight reflector and to the position of the "shutter".
If I was not confident that the installation in my vehicle was not causing problems for oncoming traffic, I would have removed them long before now - I don't like being "flashed" by oncoming traffic, and I think I've been around for long enough now to have some basic level of responsibility towards other road users.
Yes - I can certainly understand those who get upset with incorrectly installed, adjusted or maintained lights - I'm no different. But I've been around for long enough to know (from experience) that you will see far more problems coming from halogen lights poorly adjusted or maintained than you will ever see with HID (at least until HID becomes more widely used - which it will). I'm sorry, but I don't give much credibility to people who simply want all HID (or any other new technology) banned because they've had a couple of bad experiences with poorly installed or maintained lights. Fortunately, the majority don't follow this mentality, or we'd all still be driving horse & carts with candle powered lighting and an escort person walking in front of us.![]()



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