Lighting

Lighting, also called illumination, is the careful use of light to create practical or beautiful effects. It includes using both man-made light sources like lamps and light fixtures, as well as natural light. One way to use natural light is through daylighting, which means letting sunlight into buildings using windows, skylights, or special structures called light shelves. Daylighting can help save energy because buildings often use a lot of power for artificial lighting.

Proper lighting can make tasks easier, improve how things look, and even make people feel better. Inside buildings, lighting is usually done with special light fixtures and is an important part of interior design. Lighting can also be a key part of outdoor landscape projects, helping to make gardens and other outside spaces more pleasant and functional.

History

For a chronological guide, see Timeline of lighting technology.

When people first discovered fire, they used it to light up areas, like around campfires or with torches. As far back as 400,000 years ago, early humans like Peking Man lit fires in their caves. They also made simple oil lamps from natural materials such as rocks and shells, filled them with grease, and used a fiber wick to burn animal or vegetable fats for light. Many of these ancient lamps have been found in the Lascaux caves in modern-day France, dating back about 15,000 years. People also used oily animals like birds and fish as lamps by placing a wick in them, and even used fireflies for light. Over time, they invented candles and lamps made from glass and pottery. Chandeliers were an early type of "light fixture".

A big change came when people discovered whale oil for lighting. But this changed again in the 1840s when Abraham Gesner, a Canadian geologist, made kerosene, which was much brighter and cheaper. By the 1850s, whale oil became too expensive because there weren’t enough whales left, so kerosene became more popular. In 1859, the discovery of crude oil led to the start of the petroleum industry.

In the early 1800s, gas lighting became common for street lights in big cities and was also used in some shops and rich people’s homes. The gas mantle made these lights brighter. Then in the 1880s, electric lighting arrived, starting with arc lights for big spaces and streets, and later the incandescent light bulb for homes and outdoors. Electric lights became common in developed countries, changing how people lived at night and helping make cities safer.

Fixtures

Main article: Light fixture

Lighting fixtures come in many styles for different uses. They hold the light source, give direction to the light, and help prevent glare. Some fixtures are simple and practical, while others are artistic. Many materials can be used for fixtures as long as they can handle heat and meet safety rules. An important feature of fixtures is how well they turn electricity into light, measured in lumens per watt. Clearer fixtures usually work better, while shaded ones give more direction and comfort.

The color temperature of white light matters for different jobs. It is measured in kelvins and shows how warm or cool the light appears. Lower temperatures give a yellow-red light, while higher temperatures give a blue-white light. This choice is important for tasks like checking colors or showing off food and clothes in stores.

Lighting is grouped by its purpose: general, accent, or task lighting. Task lighting is strong and focused, good for reading or inspecting things. Accent lighting is decorative, used to highlight pictures, plants, or parts of a room or garden. General lighting fills in the rest, providing basic light for an area, like a lamp on a table or ceiling lights in a parking lot.

Downlighting, where lights on or in the ceiling shine downward, is very common in homes and offices. Uplighting bounces light off the ceiling to reduce glare and give even lighting. Front lighting makes objects look flat, while side lighting can cause glare. Backlighting shines behind or through an object to add depth or drama.

Indoor lighting includes many types such as alcove lighting, which is indirect and often uses fluorescent or LED lights. Soffit lighting can show off wall textures. Recessed lights, hidden in the ceiling, are popular and come in various forms. Track lighting, which can be aimed at different spots, has become popular again with safer, thinner designs. Other indoor lights include sconces, torchères, chandeliers, pendant lights, and portable table lamps.

Outdoor lighting serves many purposes like lighting up areas, advertising, and decoration. Street lights help people see roads at night, while floodlights can light up work zones or sports fields. Beacon lights guide drivers, security lights aim to prevent crime, and entry lights mark home entrances. Underwater lights can decorate ponds or pools. All outdoor lighting can add to light pollution, which harms the environment.

Fixture components

Lamps

Main article: Lamp (electrical component)

Lamps, often called "light bulbs," are the parts of a light fixture that change electricity into light. In the past, lamps were mostly judged by how much power they used, measured in watts. But now there are many types of lamps, so comparing them by watts doesn’t tell the whole story anymore. For example, an older 60 W bulb might give about the same light as a newer 13 W energy-saving bulb. The better way to compare lamps is by how much light they make, measured in lumens. A small candle gives about 13 lumens, a 60 W old bulb gives around 700 lumens, and a 15 W energy-saving bulb can give about 800 lumens.

There are several kinds of lamps:

• Fluorescent light: A tube that uses a special coating and low-pressure gas to make white light.
• Halogen: These are like old bulbs but with special gases that make them more efficient.
• Neon: A glass tube with gas inside that glows in different colors depending on the gas.
• Light-emitting diodes (LED): These are modern lights that shine by moving electrons in special materials.
• Compact fluorescent lamps: These are designed to fit in places where old bulbs used to go.

Ballasts

Ballast: A ballast is a helper part that starts and controls the power for certain types of lights, like fluorescent and strong discharge lamps. Some ballasts also help keep the lamp safe by protecting it from too much heat.

Vehicle use

Main article: Automotive lighting

Vehicles usually have headlamps and tail lights. Headlamps are white or yellow lights on the front of a vehicle. They light up the road ahead and help other drivers see the vehicle. Many car makers now use LED headlights because they save energy. Tail and brake lights are red and shine from the back of the vehicle. They show which way the car is moving. White reversing lamps at the back show when a car is moving backward. Flashing turn signals on the front, sides, and back of a car tell other drivers when the car is turning. In the late 1950s, some car companies started using special technology to light up their car’s speedometers and logos.

Lighting practice

Architectural lighting design

Main article: Architectural lighting design

Lighting design for buildings is called 'architectural lighting design'. Some designers focus on using natural light, called daylighting, or lighting outdoors, like in landscape lighting. When designing lighting for buildings, designers think about how pretty the lighting looks, how much light is needed, who will be in the building, saving energy, and how much money it will cost. They also think about how much natural light comes into a space using daylight factor calculations. For simple lighting setups, they use tables to figure out what works best. For more complicated designs, they use computer programs like Radiance to test their ideas quickly.

The colors and materials on walls and furniture can change how a room looks with light. Dark paint can make a room seem smaller and dimmer, while light paint can make it feel bigger and brighter. Shiny surfaces can also affect how light behaves in a room.

Stage lighting

Main article: Stage lighting

Lighting helps show off performers and artists in live shows like plays, dances, or musicals. It is arranged to create special effects for each scene. Stage lighting uses many tools, such as dimmers, colored filters, mirrors, lenses, and different types of lamps. These tools are adjusted for each show. A lighting plan is made so the lighting operator can change the lights at the right times during the performance. Modern cameras for movies and TV need less light and the lights used create less heat than older ones.

Measurement

Main article: Photometry (optics)

Measuring light helps us understand how much useful light reaches a surface and how much comes from a lamp or other source. We also look at the colors this light can show. Our eyes see light differently depending on its color, so special methods are used to measure light that is useful to us. The basic unit for measuring light is called the candela (cd). Other units come from this, like luminance, which tells us how much light comes from a certain area.

We also measure how much light falls on a surface, called illuminance, using a unit called lux. This helps us understand how bright something looks to our eyes. There are also ways to measure how comfortable lighting feels, such as controlling glare in rooms.

Color properties

To describe the color of light, we use two main ideas: one tells us if the light feels warm or cool, and the other tells us how well the light shows true colors. However, as new lights like LEDs become common, these ideas are being examined more closely. To get the best color showing, some experts suggest using another measure along with the traditional ones. This helps make colors look more vivid and real.

Light exposure

Special tools can measure how much light a person or object is exposed to. One small device, worn on the head, can track the light that enters our eyes. This helps scientists study how light affects our body’s natural clock, rest, and activity patterns over many days. It records light and activity at regular times and keeps this information for later study.

Secondary effects

Lighting is mainly used to help us see, but it can also affect our health and the environment. Proper lighting is important for tasks and can improve mood and performance. However, too much light or the wrong kind of light can cause problems like headaches, stress, and higher blood pressure. Bright light can make emotions feel stronger, while dim light may help people make more rational decisions.

Using natural light from windows and skylights can save energy and benefit health. Studies show that natural light can improve learning in students and help older people with memory issues. Lighting design should consider the right amount and type of light for different times of day to support healthy body rhythms.

There are many ways to save energy with lighting, such as using controls that turn lights off when not needed, choosing energy-efficient fixtures, and using natural light whenever possible. Lighting control systems can adjust lights based on time, occupancy, and available daylight to reduce energy use. Daylighting, which uses natural light inside buildings, saves energy and can improve health and performance. Solid-state lighting, like LEDs, is becoming more common because it uses less energy and lasts longer than traditional bulbs.

Environmental issues with lighting include the disposal of certain bulbs that contain harmful materials and the problem of light pollution. Light pollution occurs when too much artificial light spreads into areas where it isn’t needed, wasting energy and affecting wildlife. This extra light can harm animals by disrupting their natural patterns of activity, metabolism, and reproduction.

Main articles: Light pollution, Over-illumination, and Light effects on circadian rhythm

See also: Ecological light pollution

Professional organizations

International

The International Commission on Illumination (CIE) is an international group that sets standards for color and lighting. It creates helpful tools that many people use, like different ways to talk about color and how well lights show colors.

The Illuminating Engineering Society (IES) works with groups like ANSI and ASHRAE to make rules and guides for lighting in buildings. Companies that make lighting tools share information about how their products spread light, using formats that the IES helps create.

The International Association of Lighting Designers (IALD) supports people who design lighting and helps them learn more about their work. Designers who meet certain rules can add "IALD" to their names.

The National Council on Qualifications for the Lighting Professions (NCQLP) offers a test to check if someone knows basic lighting design ideas. People who pass can call themselves "Lighting Certified" and add "LC" to their names. This test is one of three big tests in the lighting field in the U.S., and anyone can take it, not just designers.

The Professional Lighting And Sound Association (PLASA) is a group in the UK for people who work with lighting, sound, and similar tools for shows. They help protect the interests of their members and talk to governments about rules that might affect their work.

National

• Association de Concepteurs Eclairage (ACE) in France
• American Lighting Association (ALA) in the United States
• Associazione Professionisti dell'Illuminazione (APIL) in Italy
• Hellenic Illumination Committee (HIC) in Greece
• Indian Society of Lighting Engineers (ISLE)
• Institution of Lighting Engineers (ILE) in the United Kingdom
• Schweizerische Licht Gesellschaft (SLG) in Switzerland
• Society of Light and Lighting (SLL), part of the Chartered Institution of Building Services Engineers in the United Kingdom.
• United Scenic Artists Local 829 (USA829), membership for lighting designers as a category, with scenic designers, projection designers, costume designers, and sound designers, in the United States