School taught me that "yaght" is spelled "yacht", that is education also.

The fact is, an HID capsule has a larger light source than the filament in a quartz-halogen bulb. I know, years of work in office lighting (including using ray-tracing software to design optics (lenses and reflectors) around the light source) and being in on the early designs of HID lights as an Engineer & supplier of reflectors to Visteon probably also isn't enough, ... but the halogen to HID lights and designs are significantly different and do not transfer over.

However, since US lights have a reputation for such dismal light patterns where the high-beam is controlled, and the low-beam is basically an out-of-focus beam where the filament is high and to the left of the focal point throwing a blob of light down and to the right, ... I digress, putting HID bulbs in this arrangement pretty much means a brighter blob of light low and to the right (with brighter glare). Thus the move to European-spec lights, with proper optics, and with well-distributed light. It's not just how bright the light is, it's where the light goes.

With proper optics, IE Euro lights, the low-beam typically has a sharp cutoff of light at the top, formed with the optics of the reflector & lense and based on exact positioning of the light source (filament or capsule). When the shape and size of this light source changes from a small filament to a larger capsule, so does the shape of the light output, and only the light generated in the original designed location is controlled properly, light outside of that location strays. The same thing holds true for the low-beam and fog-beam lamp designs with a mask to produce the upper cutoff.

Those without optics design education, training, and experience might or might not understand this, but I've seen millions of dollars thrown at re-designing a light to accomodate the incoming HID options on cars, because the lights designed for filament-bulbs would not pass DOT (or European requirements depending on the market).

Yes "not having enough light is illegal too", if you have non-standard, dirty, rusted, damaged, or aftermarket-smoked lights they too are illegal. Any alteration from the factory light must be tested and approved by DOT (which will also be molded into the lense) to be highway legal in the US.

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Gone to the dark side

- Jeff