LED, HID and halogen bulbs all have different light emission patterns. The housings and projectors for each type of bulb is designed to focus that light into a usable pattern. When you put a bulb into a reflector bowl or projector it wasn't designed for, it can cause a lot of glare due to scattered, unfocused light. Next time you're driving at night, you'll probably see someone with very bright, glaring blue-ish headlights. That is someone who put HID bulbs into halogen reflectors. It actually send less light down the road where you actually want it, and just scatters it all over the place, namely, into oncoming traffic's eyes.
Read up on these threads that were posted earlier, lots of good info
http://www.danielsternlighting.com/tech/bulbs/Hid/conversions/conversions.html
https://www.hidplanet.com/forums/fo...t-test?44158-HID-plug-n-play-fails-govt-test=
