A lot of people are confused because they are misinformed. A lot of people are using the colour temparature as a marketting gimmick. Now, I'll state it very clearly:
The colour temparature is measured in Kelvin(K)
The brightness is measured in lumens
The intensity is measured in Candela
Now, a lot of mechanics suggest a 8000K HID, claiming that it is brighter. Theoritically, they are trying to get you to think that the higher the K, the brighter the HID. WRONG! Kelvin is used to measure colour temparature, NOT brightness.
The 4300K HID which is used in OEM vehicles is slightly yellowish. The 6000K HID produces a brilliant white colour with a slight stinge of blue. The light produced is brilliant white. The 8000K HID is blueish colour. the 10000K HID is greenish blue and the 12000K HID is purpleish. So bear in mind, KELVIN = COLOUR. The colour temparature also in NO WAY indicates how hot the HID is operating at.
Now, some people might ask, then, which HID is brighter? Research and development has shown that the 4300K produces the best light output which is about 3200 lumens. That is why OEM cars utilize the 4300K HIDs. The 6000K HID produces about 2800 lumens of light. As you can see, all factors remaining constant, the higher the colour temparature, the lower the brightness.
There really is only 2 good HID brands out there, namely, Philips and Osram. Hella and Bosch ballasts are not bad as well. The bulbs are basically by Philips or Osram. Philips is the pioneer of the HID technology. The bulbs are produced with state of the art machine and meant for long durability. Some sellers claim to be selling 8000K Philips HID, but that's a FAKE. For your information, Philips HID is only rated up to 5800K which is marketed as the Philips 6000K Ultinon.
Why is it that they don't produce bulbs with higher Kelvin? It defeats the purpose of HIDs because anything higher would require a blue coat filter to achieve the colour effect. By doing that, brightness will be reduced dramatically and we might as well just stay on with the conventional halogen, as there is not much improvement.
As for people who has a 6000K HID coated with blue coating, they probably bought some cheap HID where the manufacturer does not have the technology to produce proper HIDs. By right, 6000K should still be achievable without coating. I myself am using the 6000K HID which is brilliant white and does not require any blue coating.
Another thing to consider is, get a high quality HID bulb as the blubs retrofitted into your headlights must have the same point as your halogens so that the lights will reflect off the reflectors at the same point as the original halogens. Screw this part up and you will get uneven light distribution which oncoming traffic will then consider as glare.
For those who use the Halogen bulbs with HID looks, a.k.a "blue bulbs". NO, THOSE ARE NOT HID. A lot of people are under the impression that those bulbs are HID. So I am going to say it again, those are just normal halogen bulbs which are just coated blue to filter off the yellow spectrum and thereby giving you the whitish blueish effect. Yes, you might get the looks but definitely not the brightness and the intensity.
I hope this post of mine here will help many of you out there in answering you questions and clearing your doubts. I love HID, and I am never going back to halogens. :D Some people might say HID is blinding. The fact is they don't know the benefits of HID and also their perception came from those who were irresponsible enough to not adjust their headlamps to ensure the beam shines the road and NOT oncoming traffic. The same goes to those halogen users who changed their bulbs but screwed up the reflected beam.
Those who have yet to adjust their headlamps, please go out, lower yourself to a seating level and look at your headlights. If you think they are a sore to your eyes, do humanity a favour, please readjust your headlamps. Thank you very much and cheers! :)
