As you know, whether from seeing cars on the road or hearing people talk, there are multiple forms of automotive lighting available. I will discuss standard halogen lighting and HID lighting as well as important terms in the following tech article. Many automotive manufacturers, including Nissan, Infiniti, Audi, VW, BMW, Toyota, Lexus, Acura, Ford, and Cadillac, use HID lighting in their factory cars so it is far from uncommon to see. Please familiarize yourself with the terms below and the simple science of how each system works. Also discussed will be the costs, advantages, disadvantages, availability, and how to of each type of lighting.
Important Terms to Know
Wattage/Watt – (w) – The measure of electrical power
Voltage/Volt – (v) – The measure of electrical charge
Ampere/Amp – The measure of electrical current
Kelvin – (K) – The measure of color temperature
Lumen – (lu) – The measure of light brightness
Candela – (cd) – The measure of light intensity
Pattern – The beam pattern of light that is projected. This includes depth and width of illumination, and angle of light dispersion.
Cut-off – A definitive line of light produced by the headlight that blocks or cuts off light above a certain level in order to prevent glare and blinding for oncoming motorists.
Halogen bulbs are currently used in most production cars and have been religiously for the past half-century. Chances are your car is using halogen bulbs. The bulbs are your standard incandescent light bulbs that operate on direct current running through a filament. The filament is fragile and is usually made out of a coil of wire created from exotic metals. This is encased in a glass bulb material and often filled with a gas. When current (or amperage) is supplied to the positive side of the circuit and travels to the bulb it crosses the coil of wire (filament) where it encounters high resistance. This resistance generates heat and thus produces light.
Halogen headlight bulbs typically operate between 55 and 85 watts. They are quite inefficient though as more heat is produced than light. Also, as the bulb ages, tungsten (the common metal that filaments are constructed out of) atoms evaporate as a result of the repeated high temperatures. The addition of the inert gas in the bulb reduces evaporation and thus increases longevity of the bulb. These atoms build up on the glass over time and are the reason burned-out bulbs often seem to have a burned grayish color to them. Eventually, it evaporates enough that the filament breaks and the bulb ceases to function. The major benefit of halogen bulbs and their accompanying lighting systems are cost. The bulbs are very cheap to replace and there are not many components to fail.
Gas Discharge or High Intensity Discharge lighting
HID lighting is very different from standard incandescent bulbs. Instead of a filament, gas discharge uses a bulb with two electrodes next to each other. HID bulbs are filled with noble gases and metal salts. These two ingredients are a major part of the lighting process. HID bulbs also do not dim nearly as much over time when compared to halogen bulbs.
A ballast powers the two electrodes mentioned above. A ballast is essentially a circuit board made up of resistors, transistors, and capacitors. This acts as an ignition of sorts to light the bulb and regulate power flow. Ballasts take a small amount of power and produce a tremendous output (generally 35w at 12v and generating 25,000v).
This power is sent to the positive electrode and creates an electrical arc across the two electrodes. This process excites the gas and causes it to discharge light (photon particles). This is where the name gas discharge comes from.
The main disadvantage to a HID lighting system is the cost. Many kits can run well over $600. 00 and replacement bulbs often run at least $50. 00. There are also more components to potentially fail in an HID system than a halogen lighting system.
A side by side comparison of Halogen and HID
HID bulbs produce roughly ten times more intense light (over 200,000cd vs. 20,000cd for halogen)
HID bulbs last eight to ten times longer than halogen bulbs (2750 hours vs. 300 hours)
HID bulbs produce at least four times more bright light than halogen (3200lu vs. 800lu)
HID bulbs use less wattage than halogen bulbs (35w vs. 55-85w)
HID bulbs produce a less visually fatiguing output than halogen (less infrared and UV light)
HID bulbs produce a higher Kelvin light, which being whiter than the output of a halogen bulb illuminates the road better.
HID bulbs have high flux properties thus distributing light more evenly.
HID bulbs produce a much wider and deeper beam pattern than halogen bulbs.
HID bulbs are much more expensive than halogen bulbs.
HID systems are very expensive when compared to halogen systems.
HID bulb options
There are two types of HID bulbs on the market today, D2S and D2R bulbs. The difference between the two is the D2R bulbs have a metallic strip along the edge of the bulb to reduce glare. The D2S bulb typically produces more light out of the two. Generally, D2R bulbs are used in reflector housings and D2S bulbs are used in projector housings. By no means is this rule set in stone though. Quite a few companies manufacture HID bulbs but the two most common in factory (OEM) cars is Sylvania or Phillips. Most manufacturers offer at least a twelve month warranty on their HID bulbs.
Color selection is a big part of HID selection. Almost all factory (OEM) HID kits are 4300K but some manufacturers use 6000K. The higher the Kelvin or K rating on a bulb, the lower the light output in lumens. Many aftermarket companies offer HID kits of 8000K, 10000K or 12000K. In my opinion, the only reason one would buy a kit with a Kelvin rating of over 6000K is that they are misinformed or uneducated in the area of lighting. Many people will try to tell you that bulbs with a high Kelvin rating (the bulbs that are very blue or purple) are brighter than those with a color of 4300-6000K. That is 100% false. For visibility purposes do not buy a kit with an extremely high color temperature. You can see below how quickly light brightness declines as color temperature increases.
Here is a chart of K vs. lu
3000K = 4000lu
4300K = 3200lu
6000K = 2900lu
8000K = 2450lu
10000K = 2200lu
12000K = 1800lu
The reason most HID bulbs appear blue
Aside from the natural color of the light at 4300-6000K, which generates a bluish hue, the projector lenses, their curvature, the reflector, etc generate the color. They work together to produce light as optically designed.
HID kit options
You have several options on HID kits. The most common approach is buying an aftermarket HID kit specific to your car and bulb type. This is very effective if done properly. Also, many people opt to pick up factory units from salvage yards and retrofit them into their car. Installing the projector housing, bulb, and ballast assembly. Kits are available for most popular applications and bulb sizes including H1, H3, H4, H7, H8, H9, H10, H11, H13, 9004, 9005, 9006, 9007, etc. Aftermarket kits are nice as they come with ballasts, wiring, bulbs, and they are often “plug and play. ”Plug and play kits do not require any wiring as the bulbs and ballasts plug into your existing headlight sockets and are a snap to install (often taking a half an hour or less!)But remember, improperly installed kits can cause excessive glare, be bothersome to other motorists, and have adverse lighting effects. Make sure you do your homework!
-Information compiled by NSRz32