Thirty years ago, your only real choice when it came to your car’s lighting system was what brand of sealed-beam headlights to use. Today, there’s a bewildering array of OEM and aftermarket headlight options that can give your car a unique and dramatic new look.

THE BASICS

Although there are many variations, most modern headlights fall into one of three categories:

Halogen lights: The most common type of OEM headlight today, halogen lights are incandescent, generating light by passing an electrical current through a tungsten filament inside a bulb filled with pressurized halogen gas. Halogen lights are brighter, last longer and have better light patterns than the old sealed-beam type they replaced.

High-intensity discharge (HID) lights: Introduced in the mid-90s, HID (or “xenon”) lights have no filament; instead, a high-voltage current arcs between two electrodes inside a bulb filled with inert gas and metallic salts, causing the salts to fluoresce. Some HID systems use separate halogen lights for the high beams, while others (sometimes called “bi-xenon” lights) have internal shutters that allow the HID lights to function as either high or low beams. HID lights are brighter than halogen lights, produce a more uniform pattern, last longer and use less power, but cost more and can create annoying glare for other drivers.

Light-emitting diode (LED) lights: Introduced by Audi on its 2010 R8 sports car, light-emitting diode headlights use a series of semiconductors that produce visible light when an electrical current passes through them. LEDs use less power than other lights, have a substantially longer life and can be arranged in many different shapes, but LED headlight systems are still extremely expensive.

Many cars now offer a choice of different headlights from the factory and there are aftermarket kits to replace halogen lights with HIDs; in the future, there will probably also be LED conversion kits. Even if you stick with halogen lights, there are replacement bulbs that mimic the distinctive blue-white glow of xenon headlights.

PROJECTORS AND ANGEL EYES

Many OEM headlights use a shallow, dish-shaped reflector behind a prismatic lens that helps to amplify and shape the light pattern. Some cars substitute compact projector lenses with a deeper, elliptical reflector that provides a more concentrated light pattern.

A popular aftermarket modification is to replace OEM prismatic lenses with projectors, often mounted in a new housing with a decorative black or chrome finish. The stock lens is replaced by a glass or plastic headlight cover, which may be clear, smoked or color-tinted to create different stylistic effects.

Another popular option is to add daytime running lights (DRLs) inside the headlight housing. The DRLs may use individual LEDs; a single LED illuminating a light strip or ring; or a cold cathode fluorescent light (CCFL). These lights may be arranged in various shapes, but the most common is the “halo” or “angel eye,” an illuminated ring around each projector lens.

UNDERSTANDING THE RISKS

Before you rush out to order a set of angel eyes for your own car, here are some important considerations:

Professional installation is a good investment: While many aftermarket headlights are designed as direct replacements for the OEM units, removing and reinstalling headlights can be a headache, with many potential pitfalls. Consider getting professional help, particularly if you’ve never installed headlights before or if the installation involves any wiring changes.

Don’t sacrifice safety for style: Some aftermarket lights are designed primarily for looks. Be careful that your new lights don’t hurt headlight performance or present a hazard to other drivers. Know the law: Many aftermarket lights are advertised as “for off-road use only” and are illegal for street use in at least some areas. Even if the lights have “DOT” markings, that doesn’t necessarily mean they’re legal for your specific car or in your area. Your best bet is to talk to the DMV or local or state police before you order new lights. Otherwise, you may be risking a fix-it ticket or worse. HID conversions are particularly problematic: The National Highway Traffic Safety Administration has declared that it is a safety hazard and a violation of federal law to replace halogen headlights with HIDs.