Very good writeup from the other site...had to cross post it over here since it comes up so often!

Quote Originally Posted by dirtyd88 View Post
Here is a tech article a buddy of mine on F150online wrote up. It's more or less to shed a little light on the parts of light modifications that some people don't know or think about sometimes.
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Here's a little write-up in response to several requests. This should be a one-swing kind of deal to help noobs know the real truths and myths about new automotive lighting.

First off, let's examine the basics of a headlight. A headlight is a pair of light-emitting devices on a motor vehicle. By law, a passenger vehicle needs to have two separate light mounts, and two separate beams, a high and low.

Overview

Low Beam

Low beam headlights provide a distribution of light designed to provide adequate forward and lateral illumination with limits on light directed towards the eyes of other road users, to control glare. This beam is intended for use whenever other vehicles are present ahead. North American SAE beam standard contained in FMVSS states that the low beam must illuminate objects up to 150 ft in front of the vehicle without causing glare to oncoming headlights. Halogen low beams emit power at 55W or 1700 lumens.



High Beam

High beam headlamps provide a bright, center-weighted distribution of light with no particular control of light directed towards other road users' eyes. As such, they are only suitable for use when alone on the road, as the glare they produce will dazzle other drivers. FMVSS states high beams must illuminate objects up to 400 feet in front of the vehicle. High-beam halogen bulbs emit power at 65W or about 2500 lumens.



In terms of light control, there are two basic ways for an automobile manufacturer to adapt both systems into one housing. The most basic and cheap to produce is a single housing using a dual-filament bulb (F-150). The second, more expensive, but better-controlling, is a separate low and high beam into one housing (Silverado/Ram).

Dual Filament

One filament is located at the focal point of the reflector. The other filament is shifted axially and radially away from the focal point. In most 2-filament sealed beams and in 2-filament replaceable bulbs of type 9004, 9007, and H13, the high-beam filament is at the focal point and the low-beam filament is off focus. The low-beam filament is positioned slightly upward, forward and leftward of the focal point, so that when it is energized, the beam is widened and shifted slightly downward and rightward of the headlamp axis.




Single Filament

A dual-headlamp housing is more efficient, in that it has two separate extreme beam patterns. The low beam, like states above has a single-filament bulb striking its own low-beam reflectors. When the high-beams are engaged, the low beam bulb extinguished and the high-beam bulb lights up its set of reflectors.



Exceptions

With projectors (see below), there are pros and cons. Like halogens, there are projectors that do both high and low beam or just low. With a high and low beam, there is one bulb in a projector lens, and the cutoff bar is raised to allow more light upward. In a single-beam projector, there is a projector and a reflector. Projector for the low-beam, and reflector for the high. The advantage to this is that halogens have a warm-up time of a quarter of a second, retaining the "Flash to Pass" ability without upgrading to the expensive, bi-xenon route (see below).



Optics

Today, there are two main ways of providing nighttime illumination. Reflectors (stated above) and projectors, which we'll get into here shortly.

Reflectors

Reflector headlights have been around for a long time, and they have a proven track record. They're design is simple: take a small light source and magnify it into a powerful beam with an array of mirrors. The housing is curved and covered with a reflective material. A bulb is mounted right in the center, and when it's on, the light strikes the reflective surface and is bounced back as a stronger, brighter and larger beam. The downside to this type of lamp, though, is that some of the light will inevitably scatter away and be lost. Almost 95% of all headlights on the roads use this design.



Projectors

The latest and greatest in automotive lighting technology is projector headlight technology. They work much like the traditional reflector optics, but with an added step. After the light bounces off the reflective surface, it travels through a lens, which focuses the light into an incredibly tight, powerful beam. Hardly any light is scattered away, so you're left with brilliant illumination and a futuristic look. Along with this focused beam, projectors also feature a cutoff that prevents blindness from oncoming drivers.



Light Source

Halogens

A halogen lamp is an incandescent lamp with a tungsten filament. Inside the enclosed capsule is an inert halogen gas such as iodine or bromine. When electricity is passed through the filament, resistance build up to a point where it glows. 20% of its energy is given off as light, as its intended use. However, 80% of its energy is given off as heat, making halogens a very inefficient light source. Despite their inefficiency, they are very (somewhat) cheap to produce and power approximately 95% of the world's vehicles today.



Xenon Gas

HID stands for high-intensity discharge, a term referring to the electric arc that produces the light. The high intensity of the arc comes from metallic salts that are vaporized within the arc chamber. These lamps are formally known as gas-discharge burners, and produce more light for a given level of power consumption than ordinary tungsten and tungsten-halogen bulbs. Because of the increased amounts of light available from HID burners relative to halogen bulbs, HID headlamps producing a given beam pattern can be made smaller than halogen headlamps producing a comparable beam pattern. Alternatively, the larger size can be retained, in which case the xenon headlamp can produce a more robust beam pattern. They are very efficient in the amount of energy converted into light, as HID headlamp burners produce between 2,800 and 3,500 lumens from between 35 and 38 watts of electrical power, while halogen filament headlamp bulbs produce between 700 and 2,100 lumens from between 40 and 72 watts at 12.8 vDC. The average service life of an HID lamp is 2000 hours, compared to between 450 and 1000 hours for a halogen lamp

Color:

The color of an HID bulb can be changed with the difference of metallic salts. They all follow the same Kelvin scale. For comparison purposes, a regular Halogen lamps burns at 3200K.



Most people believe that the higher the Kelvin, the more light output. This is false. Luminously speaking, ~3500K is the brightest color you can get. Looking on the scale above, you will see that will land in the yellowish category. Yellow is the direct opposite of a pure black environment (most people commonly believe white is the best light, this is false). This same principal also applies to a yellow chalk on a blackboard. If you Google older French or European cars, you may see some still have yellow fog lights and headlights. They were the first to discover this color trend back in the 70’s I believe. As you move up into the scale, you slowly lower luminous output. 8000K in the dark is almost the same as using a candle and anything above 10,000K is like a blacklight. You might as well just shut off your headlights and save your alternator.

Drop-ins, swaps and retrofits: Shedding light on headlight upgrades


Before we begin, we must analyze and understand what you desire and I can tell you what path to choose. I will list three things. You choose two that appeal the most to you.

Price
Quality
Appearance

Let’s say you chose appearance and quality. Sounds like you know what you are doing. You would want to do a projector with a xenon retrofit. This will be upwards of $500 (price being the one you didn’t choose), but you will have a headlight system that rivals BMW's and Mercedes'. How about price and appearance? You will most likely do the “ricer mod” and buy a cheap Chinese HID kit and drop it in place of you factory halogen reflectors. You will save money and think it looks good, but you will have glare like a 747 on final and piss everyone off. Lastly we have price and quality. That would yield you with a pair of eBay projectors. They are relatively cheap and will give you a (somewhat) decent usable light output, but they look like a$$ and won’t be as well as a true retrofit. Let’s examine each of these individually:

The cheapest of the three, HID drop-ins are basically their namesake. You buy a cheap HID kit (most likely off eBay) that was made in China in a mass-production shop, and drop them in place of your factory bulbs. There are several things wrong with this. First off, it’s illegal. That’s right. HID kits are illegal in the US. That’s why they are made in China and you can’t buy these off the shelves here in America. They are not DOT-approved. However, the chances of you getting pulled over are slim to none, and the chances of you getting anything more than a “Fix-it” ticket are 1 in a million. Technically speaking, this is the worst move you could do. A headlamp reflector is designed to use the light from a focal plane, meaning a fixed point roughly in the middle of the heat shield. An HID bulb and Halogen bulb are different shapes, lengths, and widths. Also, the point of light source of an HID bulb is one single round diode. A halogen uses a tungsten filament that is thin and long. Picture the tip of a stick on fire as opposed to the whole stick itself on fire. So in the end you will have glare and no useful light, but as long as you look cool, who cares? Typically these run from $30-$100.



Secondly we have swaps. Again, like the namesake, you simply swap your headlights for another pair. Most are found online. Some people retain the factor look and stick with the Lightning style (for you 97-03 guys) or go with dual-beam setup. Aesthetically speaking, the eBay projectors aren’t the best looking in the book (in my opinion), but they get the job done if you want cheap projectors and/or a dual-beam setup. Some people also drop in an HID kit at this stage too. This works better than a reflector setup, but again- the reflectors and focal point of a HALOGEN REFLECTOR are different than normal XENON REFLECTORS. So you still get glare or not-so-nice cutoff line. If you upgrade to knock-off reproductions, you will get a better beam line (if you stick with halogens) than the fluted-lens style of OEM, but still not as nice as OEM Lightning headlights. Typically these run $100-200.



I saved the best for last. Here is where we get into detail about projector retrofits. A retrofit is where you take a quality (but expensive) projector off a car and modify it to fit you original housing. This is the grand-daddy of all lighting upgrades. You get the quality cutoff and light scatter. you get the quality factory bulbs and ballasts. The only problem is that it's expensive and labor-intensive. You can scratch the labor intensive part and pay someone else to do it, but jack up the costs a bit more (around $200-$400 more). A basic run through means you take out your old headlight, open it up, cut a spot for the projector to fit and mount it. Aim everything, install the wiring and put it all back together. You can see the whole process here (OBS) and here (NBS). Typically these run from $300-$1500.



I hope you enjoyed this thread and any information I have provided to you as much as I enjoying gathering it all together. Sources include Wikipedia, various Google images, and several threads from F150online.com. And please, if this thread has helped you or answered some of your questions, feel free to let me know by pointing a noob in this direction if you ever see a question asked :smt023


Written and researched by Raptor05121, F150online Technical Article Contributor