Lighting systems improve visibility at night, and make a vehicle visible to other road-users.
A lighting switch operates tail-lights, park lights, and headlights, to allow the driver to see ahead. A dip switch allows the driver to change the beams from high to low, or vice-versa, as required.
Stop-lights operate when the brake pedal is depressed.
Turn-signals alert other drivers of a change in direction, and are mounted so they can be seen from the front, rear and sides of the automobile.
An emergency flasher system operates both front and rear turn-signals at the same time. Other circuits operate courtesy, or convenience lights, reversing lights, and fault indicators.
Vehicle lighting
Vehicles typically include headlights and tail lights. Headlights are white or yellow lights placed in the front of the vehicle, designed to illuminate the upcoming road and to make the vehicle more visible. Tail lights are always red and are placed in the rear to quickly alert other drivers about the vehicle's direction of travel. In the image to the right, the top (white portion) of the tail light is the back-up lamp, which when lit, is used to indicate that the vehicle's transmission has been placed in the reverse gear, warning anyone behind the vehicle that it is moving backwards, or about to do so.
In addition to lighting for useful purposes, automobiles increasingly feature ornamental lighting. In the late 60s and early 70s, manufacturers would sometimes backlight their logos and or other translucent paneling. In the 90s, a popular trend was to customize vehicles with neon lighting, especially underneath the body of a car. In the 2000s, neon lighting is increasingly yielding to digital vehicle lighting, in which bright LED's are placed on the car and operated by a computer which can be customized and programmed to display a range of changing patterns and colors, a technology borrowed from Christmas lights.
Lamps
Commonly referred to as 'light bulbs', lamps are the removable/replaceable portion of a luminaire which convert electrical energy to both visible and non-visible electromagnetic energy.
Incandescent Lamps
The incandescent light bulb was the first type of bulb, and is inefficient at converting electricity to light. About 90% of the energy input is wasted as heat. This excess heat is then dumped into the air which, in warm climates, must then be cooled by ventilation or air conditioning, resulting in more energy wastage. Due to their heat output, incandescent bulbs can cause burns or start fires if used improperly, and tend to have greater glare.
Halogen bulbs are an improved incandescent. Light energy output is about 15% of energy input, instead of 10%, allowing them to produce about 50% more light from the same amount of electrical power. The bulb capsule is under high pressure instead of a vacuum or low-pressure noble gas. As well as being much smaller and having a hotter filament temperature, this causes halogen bulbs to have a very hot surface. This means that glass bulbs can explode if broken, or if operated with residue such as fingerprints on them. The risk of burns or fire is also greater than other bulbs, leading to their prohibition in some places. Halogen capsules can be put inside regular bulbs or dichroic reflectors, either for looks or for safety.
Good halogen bulbs produce a sunshine-like white light, while regular incandescent's produce a light between sunlight and candlelight. People sometimes find them psychologically pleasing over other types of bulbs due to the more natural color, which lights skin tones and other artifacts more accurately.
Fluorescent Lamps
Fluorescent bulbs are about 40% efficient, meaning that for the same amount of light they use 1/4 the power and produce 1/6 the heat of a regular incandescent. Fluorescent's were limited to linear and a few circular ones until the 1980s, when the compact fluorescent was invented. The compacts can plug into their own fixture, or fit in to a standard screw base for self-ballasted ones. All last far longer than incandescent's, but do have some starting trouble in very cold weather when installed outside.
Fluorescent's most often come in cool white (CW), with some home bulbs being a warm white (WW), which has a pinkish tint. In between there is an "enhanced white" (EW), which is more neutral. There is also a very cold daylight white (DW) which is rather unpleasant to most people and therefore rarely used. Compact ones are usually considered warm white, though many have a yellowish cast like an incandescent. Because the above terms are entirely relative and almost arbitrary, color temperature and/or the color rendering index (CRI) are used as absolute scales of color for fluorescent's, and sometimes for other types of lighting.
HID Lamps
High-intensity discharge lighting first came about with the mercury-vapor streetlights, and later the high-pressure sodium ones with their characteristic orange color. Modern ones are metal halide, used in everything from headlights to floodlights, and with a more pleasant color balance. Like fluorescent's, all HID bulbs require a ballast, but they also require a few minutes (or seconds for headlights) to warm up after "igniting". HID bulbs are over 60% and up to 80% efficient.
LED Lamps
LED's are a very recent introduction to the market, and they are still extremely expensive for any decent-sized bulb. They do however last an extremely long time, up to 100,000 hours (compared to around 10,000 for fluorescent and 1,000 for incandescent). These have come about only since the white LED's they use, and in turn the blue LED's which they were based on. It appears that for now these will be most useful and cost-effective in smaller applications, starting with nightlight's. Colored LED's can also be used for accent lighting, even in fake ice cubes for drinks at parties. They are also being increasingly used for Christmas lights, and not just the battery-powered kind. White LED's are about the same efficiency as other fluorescent's, while red ones can be up to 90% efficient.
LED Technology for theatrical and concert applications is still in its infancy, but is advancing at an incredible rate. Patent disputes of RGB color mixing ideas are currently slowing development, despite the fact many products are being released that take advantage of red, green, blue, and sometimes white, LED's to mix color. LED technology is useful for lighting designers because of its low power consumption, low heat generation, instantaneous on/off control, continuity of colors throughout the life of the diode and relatively low cost of manufacture. In the last few years, software has been developed to merge lighting and video by enabling lighting designers to stream video content to their LED fixtures, creating low resolution video walls.
Source: CDX Global & Wikipedia - en.wikipedia.org
