HID all it's cracked up to be?

The HID pattern has a sharp cutoff. To the left of center (as viewed from the driver's seat), it is level. To the right of center, it ramps up to throw more light farther (still with a sharp cutoff). The HID pattern (for each bulb) looks something like this:

[Broken External Image]:http://www.desperado.scvnet.com/~philh/HID pattern.gif

If you park in front of a light colored wall, you will see two overlaid patterns like this. Too close, it will not look this way, but as you back up, it resolves into this pattern. The distance between the lamps (about 4 feet) is significant at close range, but after 50 yards or so the patterns from the two lamps effectively merge into a single pattern like the one above.

It has been in use in Europe for at least 30 years. The idea is to have a minimal "blank" in the pattern where oncoming cars will be, so as to avoid throwing glare into their eyes. Of course, in GB the pattern is mirrored.

Most halogens with a clear outer lens (no facets) also have this pattern. I have HIDs, so I can't verify, but I believe the Prius halogens share this same pattern.

Some American cars still use a fluted outer lens to establish the pattern, and they have the old "fuzzy blob" pattern like the old sealed beams had.