Light_Vocabulary

**Accent Lighting** Directional lighting to emphasize a particular object or draw attention to a display item.

Defined as ballast factor divided by input watts. The value is used to evaluate various lighting systems based on light output and power input. The BEF can only be used to compare systems operating the same type and quantity of lamps.
 * Ballast Efficacy Factor (BEF)**

For reflector type lamps. The total angle of the directed beam (in degrees horizontal or vertical) to where the intensity of the beam falls to 50% or 10% of the maximum candlepower value as indicated.
 * Beam Spread (Approximate)**

(LFL plug-in ballasts) A configuration with screw studs mounted on the base plate or bottom of the ballast. The screws are 3/8" inches long with a #8-32 thread size (#8-32 nut). They are mounted on a two inch center. The studs are usually used to mount the ballast directly onto a junction box plate.
 * Bottom Exit Studs (BES)**

The measure of luminous intensity of a source in a given direction. The term has been retained from the early days of lighting when a standard candle of a fixed size and composition was defined as producing one candela in every direction. A plot of intensity versus direction is called a candela distribution curve and is often provided for reflectorized lamps and for luminaires with a lamp operating in them.
 * Candela (cd)**

Windings of copper or aluminum wire surrounding the steel core in ballast. Also refers to the entire assembly comprising the inductor or transformer.
 * Coil**

A ballast that uses a "Core & Coil" assembly to operate fluorescent or HID lamps. Refers to copper windings on a steel core.
 * Core & Coil Ballast**

A lamp resembling the color of daylight, typically with a color temperature of 5500 K to 6500K
 * Daylight Lamp**

For U-shaped Fluorescent lamps, this measurement is the average distance to the outside of each leg.
 * Distance Outside Legs**

Unit used to measure frequency of alteration of current or voltage
 * Hertz (Hz)**

A measure of the luminous flux or quantity of light emitted by a source. For example, a dinner candle provides about 12 lumens. A 60-watt Soft White incandescent lamp provides about 840 lumens.
 * Lumens**

Lamps that are approved for burning in open fixtures (as opposed to enclosed fixtures which have an acrylic lens or plate glass enclosure).
 * Open Fixture Rated**

Generally refers to a compact fluorescent lamp containing 4 U-shaped tubes, i.e. Quad Biax®, as opposed to Triple Biax® (3 tubes) and Double Biax® (2-tubes).
 * Quad**

The distance between two neighboring crests of a traveling wave. The wavelength of light is between 400 and 700 nanometers.
 * Wavelength**

**LM**: originally this term stood for reflector light microscopy; however, today it means reflector luminaire manufacturer. It is a light fixture that is designed to project light downward, a characteristic that the International Dark Sky Association strongly approves of. These retro-style fixtures were originally commonly used in industrial areas; however, today the RLM-style light fixtures are used in non-industrial installations such as multi-family sites, restaurants, retail stores, and hotels in both indoor and outdoor applications.

Formulae: watts = volts x amps, P = V x I, electrical power = electromotive force x electric current.
 * Wattage**: the amount of electrical //power// consumed by a lamp or light fixture measured in “watts”. One watt is equal to the power dissipated by 1 ampere of electrical current flowing across a resistance of 1 ohm //**or**// the power produced by 1 ampere of electrical current under an electromotive force of 1 volt. One horsepower is equal to 746 watts.