Xenon HID headlights, the whole story

Everybody wants to drive safe at night, and that’s just a fact! But sometimes maybe our stock headlights aren’t giving us enough light to view far or good enough to know what’s in front of us on our way home. For many reasons from bad weather to old bulbs might be causing poor lighting performance. There is two ways to go these days, you either replace your stock halogen bulbs with some high performance halogen from manufacturers like Hella, or you can replace your bulbs with a High Intensity Discharge system (HID) also known by the gas inside the capsules, Xenon gas.


To understand the reasons why this kind upgrade is so popular we first have to understand how do the tungsten halogen bulb works and how is being used in headlights applications.

The tungsten halogen bulb its been around since the early 1930’s and is an incandescent lamp that works through a glowing filament and the light color is based in the kelvin temperature scale, the higher the operating  temperature will produce higher color temperature.

They are cheap to produce, easy to maintain and replace, but they aren’t that efficient when comes to lumen/watt ratio. Since they are based in a wire coil that gives a resistance to a electrical current and thus producing the glowing effect, that doesn’t leave much room for improvement. For example the lumen/watt ratio of the regular H11 bulb is 1200 lumen / 55w = 21.81, and they can have ratios from 10 to 30 lm/W.

High Intensity Discharge (HID) is a type of electric lamp that produces light using an electric arc between electrodes inside a transparent glass capsule. Inside its filled with metal salts and gas (xenon), the gas is what acts as a tunnel for the first spark that the ballast generates with a higher current than the operation value raising the temperature inside forcing the metal salts to evaporate and then generating plasma which increase the amount of light generated and lower the power consumption. By its operation high intensity discharge lamps are part of the family of the arc lamps.

Low Pressure Discharge lamps are just the fluorescent lights at your office or those small low power fluorescent bulbs at home. Their efficiency is pretty high, 100 lumens per watt. Other kind of low pressure lamps are sodium vapor lamps, which are the most efficient ones generating up to 200 lumens per watt, but they provide poor color rendering index with an intense yellow light that will turn the enlighten area into monochromatic black and yellow. The main application is for street lighting and applications where color rendering is not necessary.

Headlight_reflector_optics_schematicThe standard halogen reflector is quite big compared with its HID reflector counterpart, remember the average stock H4 halogen bulb will produce around 1,000 to 1,300 lumens but more important since they are designed to focus the light from that transversal glowing filament that your car maker intended you to use. Using a so-called “upgrade xenon kit” that will require you nothing more than take the halogen bulb out and replace with the xenon ones that will make it “safer to drive at night” since they produce almost 3x the light of the stock bulb.


So basically you are just putting a light source that can produce over 3000 lumens into a projector that will not only wont be able to focus the light properly and give you the improvement you want but also you will blind other drivers with all the glare you will produce, which makes it even more dangerous and irresponsible.

Properly retrofitting your headlights takes time, money and patience, that is why online stores will appeal to the lazy inside of us. In order to avoid pointing light towards other driver’s eyes, and we are not talking about the usual bright spot you see when the a car is coming, we are talking about a massive glare that will make you close your eyes and will force the pupils get smaller which is the dangerous part since it will reduce viewing distance under poorly lit roads.

Headlight_lens_optics_schematicThere is advantages and disadvantages like the halogen lamps. The most important advantage of HIDs is the high efficiency light source will have that if you do it right you will be able to raise the performance of your headlights. They are also not damaged from road vibration since there is no filament inside to break like the coil of tungsten like the halogen lamps. But once again none of this advantages will really count if you don’t project the light properly and control the glare.

Ebay Search

These days internet gives us the chance to upgrade our stock halogen lights (either headlights or fog/driving lights) with xenon lights that require no other thing than replace the halogen bulbs with the new ones, cables to connect the HID to the headlight halogen socket and a ballast that will produce the high voltage to produce the electric arc. But these are just re-based bulbs that will fit your particular socket but in most cases you will have a scatter light that wont improve anything. If you do the search on eBay of “xenon kit” you will get over 125,000 results of sellers offering you in most cases nothing more than a “kit” with a bulb that will fit your existing socket, a pair of ballast to power the xenon bulbs and a harness to convert the stock wiring to match the ballast, zip ties and misc. items .

Most of the people doing a xenon retrofit do it without knowing their stock reflectors aren’t able to direct the light produced by the HID bulb. A lot of sellers have flood internet with what they claim to be “legal retrofit xenon kits” that buyers just have to exchange the bulbs following the directions in the installation manual and they will have a “legal” high performance lights that will work just like the stock ones but with stronger light while the true story is that they are misleading people. And even tell you they are offering you Osram or Philips bulbs that are compatible with your socket, which is a total lie. Because OEM bulbs wont come in H4 or 9007 “bi-xenon” form. They are just chinese copycats that just write Philips in their bulbs so it can be sold in a higher price.


ebay-kitsOne of the most used lines to sell this kind of xenon HID kits is that they provide a light that has the color of daylight and thus give us a natural light that our eyes are confortable with. The truth is that there is no research to backup this theory, its real that with evolution our eyes adapt to see things with a light color around 5000k. But truth is that even though during the day we have pretty much everything illuminated evenly with a strong light that has a constant color meaning that our pupils don’t have to change their size for different light sources, but during the night is a whole different story! The only part of our surroundings that we can see is the things we are illuminated and the rest is just a dark environment that is out of our reach since our pupils adapt to the body of light in front of the car. And if we don’t have the correct beam pattern then we will just end up having a massive body of light in front of the car creating a hotspot making our pupils to get even smaller, and what that does is making impossible for us to see beyond the light produced by our headlights, giving us the false sensation of confidence while putting us in a dangerous position since we don’t know what it’s coming.

Massive glaring even from the side of the car

There is much more things involved into the relationship between the reflector and the bulb. Things like focus distance and light spread, are indeed necessary to direct the light properly. Think about it like if you putting your grandma’s glasses, you might see things but you wont be able to read. So even though you can see things with xenon lights, you aren’t really taking advantage of it since you don’t have the tools to do so.


Let’s explain the basics of HID and the terms involved so we are all in the same page here. I just wrote them as they came to my head so there is no particular order between them.

HID: High Intensity Discharge and also known as xenon lights that produce a more efficient light source giving you a best lumens per watt than halogen with more than twice the light with the same power consumption.

Kelvin temperature (K): is the scale used to measure the color emitted by any light source and not the temperature the bulb reaches while working, for example most of the stock halogen headlights have a 4300k color and the most popular xenon color is 6000k.

Ballast: is what drives your HID xenon bulbs creating the high voltage needed to produce and maintain the electric arc that produce the light.

Reflector: is located behind the bulb that reflects the light properly producing either low and high beams with H4 dual filament bulb or a single beam with single filament bulbs such as H11 or 9003.

Projector: is located in front of the bulb so directing the light projecting a beam pattern in front of the car but providing a proper cutoff to avoid producing glare and blinding other drivers.

Watt: scale unit for electrical power.

Voltage: scale unit of electrical charge.

Halogen: bulb with a glowing filament that has pressured halogen gas inside that prevents the filament from wearing out as it would happen in presence of oxygen.


Now that we understand the terms involved into the HID xenon systems lets keep talking.

Even though most people wouldn’t do it the right just because it takes time to get it right. And as usual the right way is the hard way, so by being lazy and cheap about upgrading your headlights or fog lights you may be the cause of accidents because of the excessive glare towards oncoming traffic and of course you will be wasting both light and money in a solution that wont provide the light pattern seen in those OEM, which takes us to the HID projector retrofit into halogen reflector.

You might end up being that moron with both headlights and fogs using HIDs glaring the world like these pictures! Scatter beam pattern and excessive glare is all you will get.



Here is a picture I took the other day with something you might want to give a thought.


And check an example of what NOT TO DO.


Now that we know what not to do, lets talk about a properly done retrofit.

We are talking about modify your headlights in order to adapt a xenon projector in them. By doing so, you will outperform both your stock halogen and plug-n-play xenon kit in lumen output and beam pattern.

The following images come from the “how to” information provided by The Retrofit Source, which is by far the only serious business into the projector retrofit with its own line of products and top notch costumer service. And the HIDplanet forum, where you will find tons of information and people that have done what you are about to do, so get real feedback really fast.

First you have to select which projector you want to use in your retrofit, in this case we will be using the FX-R from The Retrofit Source (from now on, refered as TRS) and E55-R shrouds.


Also there is a list of things you have to be ready to complete this retrofit.


One of the most radical steps you have to take in order to properly retrofit a projector is cut the bulb socket out of your reflector, from which there is no way back! This has to be made because the standard halogen reflector does not have the space or brackets to attach it. Is really important to be careful not to overcut the reflector at first, because later on after you fit the projector inside you will be able to see where you need to trim a bit more and remember the more you remove the more flexible and vibration can be an issue once is mounted in your car.


That’s because to accommodate a bigger projector that balance well with the OEM reflector you have to anchor it either with epoxy glue or custom made brackets to keep it from unwanted movements, also this way allows you to use OEM aiming knobs which will help you later on when you have the headlights back together and installed in the car so you can have a flat lateral cutoff line.

Note that im skipping some steps but im giving a link to the entire file so you guys can see the whole process and get a better idea, but for the purposes of this article I will just focus in the main steps.

After the projectors are aligned and completely attached you will need a pair of shrouds to cover the projector, this is more like an accessory to cover the projector and the hole behind and make it look stock, there is a wide selection you can use, in this case is E55-R that are based on Mercedes Benz E55 shrouds.


And at the end you will have something that looks this way.



Now lets talk about color.


Light itself provide loads of information to the brain, but is shapes and color are the main information that it provides. From there the brain do process distance and identify objects that we focus on. There is something called Color Render Index (CRI) that is how any kind of light render colors.


High rendering lights, such as the fluorescent 5400k bulbs used in photography are perfect to begin with because they render colors exactly they way they are so blue looks blue and green looks green. In other hand, sodium vapor lights have horrible CRI since they project an intense orange-yellowish light that turn the world into black and yellow so red looks black and blue looks whiteish. But color is the kind of information that helps the brain take decisions faster, so the better the CRI you get out of the headlights the better quality of information so is easier for you decide whether if it’s a rock or fruit, imagine you are under heavy rain and this is where having the right color comes handy. So choose the right color and be safe.

For headlight applications best known color is the stock halogen 4300k, and actually stock xenon bulbs used in high end cars such as BMW and Mercedes-Benz use that color aswell, it gives the best ratio of lumens per watt that our eyes can see, even though 5000k (pure white) have better CRI. Note that Osram does produce bulbs that produce higher color temperature than 4300k.

Those cheap chinese bulbs mostly are designed to handle 35W, but they market them also as 55W bulbs and by doing that it shortens the life of the bulb by almost a half. And of course they might be a color when they are brand new but with time the color will shift towards the bluish colors because the salts aren’t as pure as Philips or Osram, and the electrode construction is rubbish. So with time they will shift and maybe in different way so one side will be whiter and the other bluish, remember you always get what you pay for.

Color is also important here because xenon bulbs are available in a variety of colors that are intended more as a aesthetic feature than actual lighting. In this case the optimal colors are between OEM pale white 4300k and bluish white 6000k. As you go higher you start losing lumens because human eye cant see ultraviolet colors and the same as you go lower and getting closer to infrared light, in fact the 3000k yellow fog lights produce almost the same amount of lumens as the 5000k counterpart.


This graphic shows the actual lumens that our eyes can see in a particular color light, and as you see after 6000k you lose way too much light to be considered an upgrade for stock halogen bulbs, some people are misled to the point where they think its ok to go blue. Other colors include purple, pink and even green (krypton green) but those colors are more for aesthetic than performance.

In the case of fog lights they are traditionally 3000k yellow light, but there is a little misunderstanding there about the yellow color.

Thing is that even though a yellow glasses will improve visibility, it doesn’t work the same way when instead of filtering light you project a colored light towards a dark environment. Some might claim that yellow actually works but the truth about the yellow lights is a little different. Back in the early XX century when lighting was still transitioning from street and home lighting to automotive, back then they were yellow and the current 4300k bulbs were the novelty and actually expensive to produce. So when auxiliary fog lights were needed they selected the yellow ones for two main reasons, they were way cheaper and since they were meant to be used as auxiliary lighting, was not worth it to put expensive bulbs for an application that was not meant to be used all the time. But as decades advanced and lighting technology helped to lower the price in halogen bulbs to a point where there is almost no room for improvement. But the fog lights in most cases stayed yellow, not because they provide better lighting under fog but because they didn’t wanted change it. That was until the last decades of XX century most of automakers changed to 4300k halogens, so after that the aftermarket started to offer yellow fog lights for those believing they could achieve better results with it. In fact what most aftermarket manufacturers do is put a yellow lens in front of a standard white light so by doing that they decrease the light output by around 20 to 30%. Because fog droplets reflects light everywhere, thus lowering the performance of lighting by decreasing the viewing distance under either fog or extreme bad weather.

The claim that yellow light have a such a longwave that could pass through  the thin fog droplets and give better penetration than white light, but there is much more in the fog light operation than just the color itself. But in fact fog droplets are big enough to reflect all colors of light. One thing that yellow does well like in the sodium vapor is increase the contrast by washing out all the color and leaving everything in a yellow-black environment which under certain situations may improve driving but as I said before color is such an important information that we need in order to take the correct choice.

Because fog hovers around 18 inches off the ground the fog lights are usually in a lower position in the front bumper. So by projecting light in such a low level it can achieve penetration further in a fog free zone increasing viewing distance. And in none of these facts the light color plays an important role. So if you want yellow or white is up to you and to be honest I rather get a white light and get more performance than an increase of contrast.


Another cheap solution for get better output using the standard halogen projector is using high performance halogen bulbs, that way you will improve the lighting by 15 to 20% with the same power consumption, is really good and cheap option for those that might be frighten by the whole DIY part of the retrofit. But at least you will be doing it the right way and not glaring the world since it will provide you a proper beam pattern.


This is it for now and I really hope this information helps people out there that have been thinking to upgrade their headlights and have been looking online for those xenon kits to stay away from them and do it the right way or leave it as it is right now.

Here are some relevant links to get information about.

The Retrofit Source
Daniel Stern Lighting
How aim headlights
CoolBuls FAQ
Headlamp definition by wikipedia 

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A pair of ballast to power the xenon bulbs and a harness to convert the stock wiring to match the ballast. The xenon bulbs are available in a variety of colors that are intended more as a aesthetic feature than actual lighting

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