Headlight cover lens yellowing? Or projector cut-off coloration?

[SteveYem]

A few months ago I installed a set of Philips Xtreme Vision 4800K HID bulbs into my OEM e-code headlights and since then I have noticed increased yellow/brown coloration at the cut-off line of the beam pattern. The bulbs are noticeably brighter than the stock bulbs. More recently (over the past month), I have noticed that the overall output is less white / more yellow (closer to the stock bulb output) than before. When I started investigating what could be causing the yellow coloration, I noticed that there is a yellowish ring appearing on the inside of the headlight housing clear lens cover when the headlights are on. It's definitely on the inside because the outsides are wiped clean. My thought last night was "oh shit, the Xtreme Vision bulbs are putting out too much heat and causing the plastic lens material to burn, resulting in this yellow ring!". So, I grabbed a spare OEM headlight assembly which has a stock bulb in it, and has never had an aftermarket bulb in it, and noticed the same type of yellowish colored ring appearing on the inside of the lens. So I think I have ruled out the idea of the brighter aftermarket bulb causing damage to the lens.

Has anyone else experienced this phenomenon and, if so, is there a known fix? Is it a matter of disassembling the headlight covers to clean and/or polish the inside of the lens?

Side note - when the bulbs are first ignited, they put out a very nice white color, with only slightly yellowed cutoff, but after a few seconds they settle into the light output shown below.

Note - this discoloration is occurring on both passenger and driver side headlights, but I only photographed the driver side for the sake of this discussion.

A few different photos of the same headlight and bulb (I'm bad at photography so I wanted to get multiple representative shots).




Demonstrating the cut-off pattern about 2 feet in front of car:


Beam pattern showing the yellow/brown coloration at the cut-off line:


Interesting experiment - I placed my hand on the headlight housing lens such that I was partially covering the beam pattern at the top, and it blocked out some of the light (obviously) while also eliminating the yellow/brown color and resulting in the blue/indigo cut-off that is found on most HID headlights of cars in this league. But this is just a side point of interest and not the focus of my discussion:

[whiped]

Twins. Only pic I have handy from when I was aligning them:



They are way off again from pulling the bumper a bunch so I will play with them tonight and let you know.

I still have my stock bulbs so I will try those too.

FWIW, they are very bright though

[SteveYem]

Twins. Only pic I have handy from when I was aligning them:



They are way off again from pulling the bumper a bunch so I will play with them tonight and let you know.

I still have my stock bulbs so I will try those too.

FWIW, they are very bright though

Yep, definitely brighter than stock. And, I would even say the light output is a bit "whiter" than stock - however, the discoloration apparent on the lens cover and the (resulting) discoloration at the cut-off is more pronounced with the Xtreme Vision 4800k bulbs.

[MRPANDA]

My experience with the Phillips bulbs is the same. Great light output - but nowhere near as clear or blue of a color spectrum as most HID equipped cars.
A stock E-class with projector headlights looks much "bluer" and frankly nicer. That said, the light output is something I'm not willing to give up.

I tried the DAMA bulbs - which were definitely "bluer" - but they sacrifice too much light output for me to justify. The light output is about the same as stock, while giving off a nicer color.
D3S - DAMA Kanji Ultimate Vision 5500K HID BULBS

About the same time that I got the Phillips bulbs for the S4, I got the "Osram 66240CBI Xenarc CBI" for my old Infiniti G35 - which has projector headlamps that are close to a decade old now. The light output is about the same as the Phillips bulbs, and color is much "bluer" - the difference is start. I would imagine a lot of that is due to our projector and lens design.

[SteveYem]

My experience with the Phillips bulbs is the same. Great light output - but nowhere near as clear or blue of a color spectrum as most HID equipped cars.
A stock E-class with projector headlights looks much "bluer" and frankly nicer. That said, the light output is something I'm not willing to give up.

I tried the DAMA bulbs - which were definitely "bluer" - but they sacrifice too much light output for me to justify. The light output is about the same as stock, while giving off a nicer color.
D3S - DAMA Kanji Ultimate Vision 5500K HID BULBS

About the same time that I got the Phillips bulbs for the S4, I got the "Osram 66240CBI Xenarc CBI" for my old Infiniti G35 - which has projector headlamps that are close to a decade old now. The light output is about the same as the Phillips bulbs, and color is much "bluer" - the difference is start. I would imagine a lot of that is due to our projector and lens design.

Thanks for chiming in. Regarding your last sentence, I got lost there....I presume you meant that the difference is stark, not start? And can you clarify that you mean the light output and color of the Osram Xenarc bulbs is whiter/bluer than the Philips bulbs but has similar brightness output?