Originally Posted by hawkeye18

Yeah, 8000k is a deep deep blue that seems bright because the color receptors in our eyes are most sensitive to the color blue. You might think "well if they're most sensitive to blue, wouldn't blue be brightest?" The answer is no, because the blue receptors in our eyes are also at the edge of the receptor field, which makes it the most difficult light to focus on. This is why blue light always glares in our eyes, moreso than any other color.

Now in addition to this, consider the following: the arc of an HID outputs pure light, which means the light contains all wavelengths of light, from deep red to indigo and everything inbetween. This is why 4600k lights output the most light, because the color strikes the closest balance of all the wavelengths. The higher in color you go, the more light gets filtered out.

Think of it this way. Imagine you have a line of people, of all different colors. Red people, yellow people, blue people, green people. Now imagine you just let all of them run down a field. This represents the photons coming out of a pure white HID light. All of them come out, and photons are what our eyes pick up. Now, imagine you tell the red, yellow and green people that they can't go, and you only let the blue people go. Now the field is full of blue people, but only 25% of the people are there as compared to when you let everybody go. See what I'm getting at? The light is bluer, but there's less of it.

This is why factories produce 4600k bulbs in their cars; 4600k is akin to letting everybody go down the field. Starting at about 5000k, you start holding people back. The higher in kelvin you go, the more people you're holding back.

And this is why I will hate you forever if you get 8000k bulbs.