Since I don't like answering questions more than say, 17 times a day.. I thought it would be beneficial for everyone (and myself) to be inspired by info. writeups on various topics. Plus, there are way too many misguided people on the road. I can tell, because they blind me all night long, and I drive 2 hours at night every day for work.
That said, this is the last page you will need to learn about how HID's work.
http://www.intellexual.net/hid.html
Even if you know HOW they work, make sure you are the smart guy you think you are.. and give it a once over. The reason I think this is important is because there are people trying to imitate HID lights, and they think:
a)their high watt blue halogens are just as good, or
b)spend WAY too much money on 8000k HID lights, which arent good for two reasons:
1) They have not been engineered even 1% the amount of time that Mercedes, BMW, Lexus, and more, HID systems have been.
2) 8000k is extremely and obscenely high of a color temp rating. There is a reason that the REAL HID's use 4100k
OK, so I lied, and am not smart enough to write the long pages that another helpful member does, but here are some commonly unknown facts to know and remember about HID systems:
1. Higher temp bulbs (8000k) are NOT brighter. Kelvin is a measure of color in bulbs, and 4100k has been proven to have the brightest output and least glare of all colors in the visible spectrum.
2. HID systems are NOT blue. There is a tint to HID systems if you look at it from certain angles on the road. You will notice that directly onto the road is a WHITE color.
3. Blue isn't a good color to project. It is proven to increase glare, and has hurt my eyes today because some chevy had some 100 watt BLUE bulbs glaring in my eye from directly behind.
4. Aftermarket HID systems are not as good as the real ones. There are so many hours into designing the reflector bowl for example, it's not even funny. You will not replicate these systems without a retrofit.
That's all I have for now... I hope you've learned something from the site. Everything here is said there, and I take no credit for any original material. I learned all I know, above, from sites like these. I also happen to be friends with a guy who works with 200,000 dollar projectors for projects similar to the Emmyls, MTV video awards, etc... and know that there is more, but you have to start somewhere in learning about light.