just to give you an example, here's a comparison between running HID bulbs in halogen reflectors vs HID bulbs in proper HID projectors. pay attention to the cut off line. notice that there's no light above the cut off line in the projector HID system. you'll also notice that the proper HID system has a lower cut off line on the left side. this is to prevent the light from hitting oncoming cars. in asia, the lower cut off line is on the right side because they drive on the other side of the road.
HID in halogen reflectors:
HID bulbs in HID projectors: