Lighting FAQs

Lighting is an important design element in the creation of the atmosphere for your project and can set a mood that creates a sense of comfort. Warm tones, contrast, and functional light levels can are important design elements that can help create sociable and welcoming environment. Here are a few Frequently Asked Questions about lighting, and some common lighting terms used in the industry. For more information on lighting education visit: iesna.org

What is the difference between Footcandles and Lumens?

A footcandle (FC) is the unit of illuminance (light falling on a surface) when the foot is taken as the unit of length. One lumen uniformly distributed over one square foot of surface. One lumen falling on one square foot equals one footcandle. Lumens are the SI unit of luminous flux (unit of light output). Lumens represent the time rate of transferring luminous energy; quantity of light. One lumen is the light flux falling on a surface of one square foot, every part of which is one foot from a point source having a luminous intensity of one candela in all directions.

What is color temperature, and how does it indicate to the color of the light output from a lamp?

Color temperature (or correlated color temperature, CCT) is a number indicating the degree of yellowness or blueness of a white light source. Measured in kelvins, CCT represents the temperature an incandescent object (like a filament) must reach to mimic the color of the lamp. Yellowish-white (warm) sources, like incandescent lamps, have lower color temperatures in the 2700K-3000K range; white and bluish-white (cool) sources, such as cool white (4100K) and natural daylight (6000K), have higher color temperatures. The higher the color temperature the whiter, or bluer, the light will be.

How is quality of light determined?

Quality of light is determined by the relationship between the color temperature of the light, and the color rendering index. The color temperature indicates the appearance created by the light source. The higher the color temperature, the "cooler" the color. Typically, color temperatures of 2000K -3000K create a warm (yellow) appearance; above 4000K are cool (blue) in appearance. Between 3000K and 4000K are considered intermediate and tend to be preferred. Color rendering index (CRI) rates a light source's ability to render colors in a natural way, based on a scale from 0 to 100. In general, light sources with high CRI (80-100) will make people and things look better than those with lower CRIs.


Lighting and Industry Terms


Accent Lighting
Localized and directional lighting used to highlight, focus attention or dramatize a room or outdoor space. As part of a decorating scheme, it is used to spotlight paintings, houseplants and other possessions, or to highlight the texture of a wall, drapery or outside landscaping. Accent lighting requires at least three times as much light on the focal point as the general lighting around it.

Architectural Lighting
This broad term generally refers to built-in fixtures, such as downlighting, valance lighting or a luminous ceiling. Some people also include functional lighting, such as track or simple fluorescent, which has an architectural appearance.

Average Rated Lamp Life
T he number of hours required for half of a large group of lamps to fail or burn out. The actual life of any lamp or small group of lamps will typically be different from the average rated life.

Ballast
Electrical or electronic component required for fluorescent (and HID) lamps. Ballasts provide enough voltage to start the lamp and then limit the current for continuing operation.

Base
The end of the lamp that inserts into a lamp socket. The end or ends of a lamp that makes electrical and mounting connections.

Brushed Finish
Satin or lightly textured finish, usually on metal, produced by brushing with a wire wheel or buffing with a fine abrasive.

Built-In Lighting
Built-in lighting generally refers to lighting equipment mounted into coves and cornices, behind valences, or integrated into furniture and bookcases.

Bulb
The everyday term for an incandescent lamp. Also refers to the outer glass envelope of the lamp.

Color Temperature
The appearance of white light in terms of warmth or coolness.

Cove Lighting
Light built into a cove, a shelf or ledge at the upper part of a wall, to illuminate the ceiling. Typically fluorescent, cold cathode or low voltage strip.

Damp Location
UL listing for fixtures used in a moist unexposed area, such as a bathroom or porch area.

Deck Lights
Deck lights typically mount to the outside of a home or to the railing of a wooden deck. Since they are located near where people sit, good shielding and proper mounting height are important to reduce glare.

Diffuser
Light control device that spreads light by scattering it. Opal glass and plastic, etched glass, fabric and paper shades act as diffusers.

Dimmer
Control that varies the output of the light source by reducing the voltage or current to the lamp.

Direct Lighting
Lighting that casts all, or at least 90%, of its light downward. The term can also refer to the distribution of light or the fixtures that produce this type of lighting. With intense beams, direct lighting is very dramatic, rendering forms and textures well. Typical fixtures include recessed lights, track lights, some pendant lights and task lights.

Extended Life Lamp
Incandescent lamp with 2500+ hours of rated average life and reduced output; uses a stronger filament.

Filament
The tightly coiled tungsten wire of an incandescent lamp; glows to produce light when electricity flows through it.

Fluorescent Lamps
Lamps which operate by creating an electric arc inside a gas-filled tube. The colour of the light is determined by the type of phosphor coating used in the lamp.

Footcandles
Unit of illuminance (light falling on a surface). One lumen falling on one square foot equals one-foot candle. Also, a measurement of the amount of light reaching a subject.

G Lamp
Globe-shaped incandescent, generally for exposed use.

General Lighting
Also known as ambient lighting, general lighting provides an area with overall, non-specific illumination. General lighting radiates a comfortable level of brightness, enabling one to see and walk about safely. It can be accomplished with chandeliers, ceiling or wall-mounted fixtures, recessed or track lighting or with outdoor fixtures.

Glare
Bright lighting that causes discomfort and impairs good visibility. Possible causes may be light sources that are too bright for the application, or fixtures that may not conceal bulbs sufficiently, among many others.

Grazing Light
Directional light at an acute angle, which emphasized texture. The sources of grazing light must be close to the surface. See also Wall Grazing.

Halogen Lamp
Incandescent lamp with halogen gas fill and a quartz glass capsule. The quartz capsule requires a separate glass shield or enclosure. Due to the halogen cycle, halogen lamps operate at higher internal temperatures, producing more lumens per watt and brighter light than ordinary incandescent; lamp life is also extended. Halogen lamps include A, MB, T, PAR and MR types.

Incandescent Lamp
Produces light with a wire filament, which create light as it is heated by electric current.

Indirect Lighting
Lighting that directs all or most light upward for ambient or general illumination; comfortable illumination with few shadows.Typical fixtures include uplight cans, fluorescent lighting aimed up, track lights aimed up and torchieres.

Junction Box
Enclosure that protects spliced wires and supports surface fixtures, such as wall fixtures or ceiling fans. Also called an outlet box.

Kelvin
Scientific unit of temperature. Colour temperature is measured on the Kelvin scale.

Kilowatt Hour
KWH. A unit of measurement for electrical energy. One kilowatt hour equals 1000 watts of energy used for one hour.

Lamping
Equipping a fixture with a lamp.

LED
Light Emitting Diode. A small, solid state device used to indicate dimmer or control status; also used in signs and control units.

Lighting Controls
Devices which give you flexibility, decorative effects and multiple uses from your lighting sources. Today's sophisticated dimming systems enable you to lower the light level to conserve energy and increase bulb life; vary the mood of a room; alter light source intensity; create lighting scene in each room. Types of controls include integrated dimming systems, touch dimmers, slide dimmers and rotary dimmers.

Light Distribution
Pattern of light produced by a fixture, or created in a room.

Light Sources
The performance of any light fixture depends on the light source, or bulb, that's used. Different sources produce different effects.

Low Voltage Fixtures
Task, linear or accent lighting products for low voltage lamps. A transformer is required for these fixtures and may by integrated, local or remote.

Low Voltage Lamps
Incandescent lamps that operate at 6, 12 or 24 volts. Low voltage lamps require a step-down transformer to reduce the voltage from the normal household 120 volts.

Low Voltage Lighting System
A type of lighting that operates on 12-volt or 24-volt current rather than the standard 120 volts. Power is supplied by a transformer, which is itself connected to 120-volt power.

Lumens
The amount of light that a bulb produces. Unit of output; technically "Luminous flux."

Motion Detector / OC sensor / Occupancy Sensor
Control that uses passive infrared or ultrasonic detection to sense whether someone is present or not, and to turn a light on or off appropriately. Commonly used in outdoor flood or spot fixtures. "Automatic On" sensors turn lights on when presence; "Manual On" sensors require you to press a switch. Both types turn lights off automatically when they no longer sense a presence.

MR Lamp
Multi-facet reflector lamp, of which the most popular is MR16. MR lamps surround a halogen capsule with a computer-designed glass, or metal reflector with many surfaces or facets. These compact lamps require a glass cover, either integral or with the fixture.

Outdoor Lighting
Any hard wired, low-voltage or solar powered lighting system that is used in an exterior space. Outdoor lighting can enhance the beauty of your home, making it safer and more secure. Outdoor lighting typically is an investment that pays off in the value it adds to a home.

Photocell
Light-sensitive device used to operate fixtures according to available daylight. They are used in solar lighting and to turn outdoor or security lights on and off at dusk and dawn.

Quartz Lamp
Or quartz halogen. Term derives from the quartz glass that encloses the filament and halogen gas. Quartz glass can withstand the high pressure of the halogen lamp, but it transmits more UV radiation than ordinary hard glass. Touching the quartz glass with bare hands leaves an oily residue that greatly reduces lamp life.

Rated Lamp Life
The point in hours where 50% of a lamp type initially started will still be functioning.

Reflector
A piece of material with a reflective surface that directs light in a desired direction. Reflectors are frequently specular, but may also be glossy, diffuse or matte.

Re-Lamping
A project where the existing lighting fixtures in a home or office setting are cleaned and new lamps installed.

Retrofit
Upgrading a fixture, room or building by installing new lighting fixtures, parts or equipment.

Satin Finish
Slightly textured or brushed surface having a fine grain that reflects light with some diffusion.

Scallops
The arch or scallop-shaped pattern from a light fixture.

Silhouetting
Accent lighting technique that creates a dramatic outline by back lighting. Also used in landscape lighting.

Soffit
In architecture, the underside of an overhead component, such as an arch, cornice, beam or balcony. Often used to describe an area of the ceiling that drops below the primary surface.

Solid State
Electronics that use semi-conductor chips and circuitry.

Specialty Lighting
A broad term referring to everything from line and low voltage strip lights to special display or controlled lighting as seen in retail and commercial applications.

Specular Finish
Highly polished and mirror-like. Semi-specular finish is generally bright, but without a well-defined mirror image.

Stainless Steel
Stainless steel resists corrosion and has a rich, deep lustre. It is particularly used in bathroom and kitchen settings for a clean, contemporary look.

Step Lights
Step Lights are recessed into walls and stairs so they illuminate the treads of stairs or pathways. An eye shield is often used to block direct view of the light source.

T-Lamp
Tubular Lamp; may be incandescent, halogen or fluorescent.

Task Lighting
Light directed to a specific area or surface that provides illumination for visual tasks, such as reading, sewing or cooking. It can be provided by recessed and track lighting, portable lighting or pendant lamps. Task lighting should be free of distracting glare and should be bright enough to prevent eyestrain.

Timer
Device that turns lights on and off at pre-programmed times.

Torchiere
Indirect floor lamp that sends all, or most, of its light upward.

Transformer
A device used to raise (step up) or lower (step down) the electric voltage. For example, many halogen ceiling fixtures require a transformer to function properly. Step down transformers reduce household voltage (120 volts) to low voltage used in accent and landscape lighting. Larger transformers reduce high voltage used for efficient power distribution to safe and flexible household voltage. Input voltage is on the primary tap; output voltage on the secondary tap.

Trim
Sometimes the edge or visible part of a recessed downlight; as in "white trim". Sometimes the finishing section of the recessed fixture; as in "housing and trim."

Troffer
Recessed fluorescent fixture for use in a suspended ceiling; derived from the words "trough" and "coffer."

Tungsten-Halogen Lamp
A gas filled tungsten incandescent lamp containing a certain amount of halogens that intensifies the light source. More commonly referred to as "Halogen" lighting.

Undercabinet Fixtures
Fixtures which are placed under a cabinet or room recess to provide task and accent lighting. Under kitchen cabinets they can light a countertop with task lighting. In a display cabinet they can be used to illuminate a prized collection. They include slim, energy-efficient fluorescents, miniature track lighting and strips of low-voltage mini-lights.

UL / ETL /CE
Underwriters Laboratory. Commonly referred to as "UL". An independent organization whose responsibilities include rigorous testing of electrical products. When products pass these tests, they can be labeled and advertised as "UL Listed". UL tests for product safety only.

Ultraviolet Light (UV)
Light that is shorter in wavelength and higher in frequency than visible violet light.

Valance Lighting
A fixture installed behind a horizontal shielding over a window or along a wall. Light is distributed up and down, usually from a fluorescent source.

Volt
Unit of electrical force or pressure. Household voltage in the UK, nominally 240V, varies between 220V and 250V. Household voltage in the United States, nominally 120 volts, varies between 110 and 125 volts.

Voltage Drop
Difference in voltage along a circuit. Voltage drop becomes a problem with low voltage wiring and small cable, reducing the intensity of the lights at the far end of the cable.

Watt
A unit of electrical power.

Wattage
The amount of electricity consumed by a bulb.

Xenon
A heavy, colorless, and relatively inert gaseous element that occurs in air as about one part in 20 million by volume. Xenon Lamps are often used for under cabinet and cove lighting systems.