BU3 - LIGHTING AND ILLUMINATION FUNDAMENTALS

Zonal Cavity Method/ Lumen Method/ Flux Method

A procedure in lighting design used to determine the number and types of lamps or lumianires required to provide average level of illumination on a workplane; takes into account both direct and reflected light flux

High Power Factor

A ballast with 0.9 higher rated power factor, which is achieved by using a capacitor.

Normal Power Factor

A ballast/ lamp combination in which no components have been added to correct the power factor, making it normal (essentially low, typically 0.5 or 50%)

Light

An artificial source of illumination; electromagnetic radiation that the unaided human eye can perceive, having a wavelength in the range of 370 to 800nm

Parabolic Aluminized Reflector Lamp

An incandescent, metal halide, or compact fluorescent lamp used to reflect light from the source using a parabolic reflector.

Luminaire

A complete lighting unit consisting of one or more lamps together with components which are used to distribute light, to position and protect the lamps to the electric power supply;also called a lighting fixture

Refractor

A device used to redirect the light output from a source, primarily by bending the waves of the light

Light Loss factor

A factor used on calculation illuminance after a given period and under given condition. Also known as maintenance factor

Lay-in troffer

A flourescent fixture; usually a 2' x 4' fixture that sets or "lays" into a specific ceiling grid.

Instant Start

A fluorescent circuit that ignite the lamp instantly with a very high starting voltage from the ballast. Instant start lamps have single pin bases

Low Pressure Sodium

Considered a monochromatic light source.

Mercury Vapor Lamp

Emits a blue-green cast of light.

Tungsten Halogen Lamp

A gas filled tungsten filament incandescent lamp with a lamp envelope made of quartz to withstand the high temperature. This lamp contains some halogens (namely iodine, chlorine, bromine and fluorine) which slow the evaporation of the tungsten. Also commonly called a quartz lamp.

High Pressure Sodium Lamp

A high intensity discharge lamp whose light is produced by radiation form sodium vapor (and mercury)

Low Voltage Lamp

A lamp (typically compact halogen that provides both intensity and good color rendition.

High Output

A lamp or ballast designated to operate at higher currents and produce more light

Fluorescent Lamp

A light source consisting of a tube filled with argon, along with krypton or other inert gas. When electrical current is applies, the resulting arc emits ultraviolet radiation that excites the phosphors inside the lamp wall, causing them to radiate invisible light.

Low Pressure Sodium

A low pressure discharge lamp in which light is produced by radiation from sodium vapor.

MR-16

A low voltage quartz reflector lamp, only 2" in diameter. Typically the lamp and the reflector are one unit, which directs a sharp, precise beam, of light

Luminaire Efficacy

A measure of the effectiveness with which a light source converts electric power into luminous flux

Efficacy

A metric used to compare light output to energy consumption; measured in lumens per watt. Similar so efficiency but is expressed in dissimilar units.

Room Cavity Ration

A number indicating the proportions of a room cavity, calculated from the length, width and height of the room

Constant Wattage Autotransformer Ballast

A popular type of HID ballast in which the primary and secondary coils are electrically connected, Considered and appropriate balance between cost and performance

Constant Wattage Ballast

A premium type of HID ballast in which the primary and secondary coils are isolated, It is a high performance, high loss ballast featuring excellent output regulation.

High Bay

Pertains to the type of lighting in an industrial application where the ceiling is 20 feet or higher. Also describes the application itself

Beam Angle

The angel between two directions for which the intensity is 50% of the maximum intensity, as measure in a plane through the nominal beam center line.

Critical Angle

The angle at which light undergoes total internal reflection

Brightness

The attribute of visual perception in accordance with which a surface appears to emit more or less light

Brilliance

The clarity, strength and brightness of a color.

Visible light

The combination of the colors of the visible spectrum: red, orange, yellow, green, blue, indigo, violet.

Illuminance

The density of luminous flux incident on a surface; the quotient of the luminous flux divided by the area of the surface when the latter is uniformly illuminated

Contrast

The difference between an object and its background

Zenith

The direction directly above the luminaire (180-degree angle)

Luminescence

The emission of light to directly ascribable to the incandescence

Inverse square Law

The inverse square law states that the illumination E at a point on a surface varies directly with the intensity of I of the surface and inversely with the square and the point of the distance d between the source and the point.

Work Plane

The level at which work is done and at which illuminance is specified and measured

Illumination

The luminous flux density incident on the surface. Usually expressed in lumens per square meter.

Luminosity

The ratio of luminous flux to the correspindung radiant flux at a particular wavelength; expressed in lumens per watt.

Emissivity

The ratio of radiant energy emitted by a body to that emitted by a perfect black body. A perfect black body has an emissivity of 1, a perfect reflctor an emissivity of 0.

Reflectance

The ratio of reflected light to incident light

Coefficient of Utilization (CU)

The ratio of the luminous flux (lumens) from luminaire, calculated as received on the work plan to the luminous flux emitted by the luminare's lamp.

Luminance Contrast

The relationship between the luminance of an object and the luminance of the immediate background.

Glare

The sensation produced by a luminance within the visual field that is sufficiently greater that the luminance to which the eyes are adapted. May cause annoyance, discomfort or loss of visual performance or visibility

Recessed

The term used to describe the door frame of a troffer where the lens or louver lies above the surface of the ceiling

Troffer

The term used to refer to a recessed fluorescent light fixture

Lighting

The various processes, systems, forms and/or equipment used to provide light and illumination.

Lens

Transparent or translucent medium that alters the directional characteristic of light passing through it. Usually made of glass or acrylic.

Nadir

Vertically downward directly below the luminaire or lamp; designated as 0 degrees.

T12 lamp

Industry standard for a fluorescent lamp that is 12 one-eights (1inch) in diameter

Ambient Lighting

Lighting throughout an area that produces general illumination

Color Rendering Index (CRI)

A scale of the effect of a light source on the color appearance of an object compared to its color appearance under a reference light source. Expressed on a scale of 1 to 100. where 100 indicate no color shift a low CRI rating suggests that the colors of objects will appear unnatural under that particular light source.

Compact Fluorescent

A small fluorescent lamp that is often used as an alternative to incandescent lamp. The lamp life is about 10 times longer than incandescent lights and is 3-4 times more efficacious.

Point Source

A source of essentiality zero dimension that radiate light uniformly in all directions

Color Temperature

A specification of the color appearance of a light source, relating the color to a reference source heated to a particular temperature, measure by the thermal unit Kelvin. The measurement can also be described as the 'warmth' or 'coolness' of a light source.

Metal Halide

A type of high intensity discharge (HD) lamp in which most of the light is produced by radiation of metal halide and mercury vapors in the arc tube.

Mercury Vapor Lamp

A type of high intensity discharge (HD) lamp in which most of the light produced by radiation from mercury vapor.

Luminance meter (brightness factor)

A visual instrument or photoelectric instrument used to measure luminance.

LED

Abbreviation for Light Emitting Diode. An Illumination technology used for exit signs. Consumes low wattage and has a rated life of greater than 80 years.

NEMA

Abbreviation for National Electrical Manufacturers Association

NIST

Abbreviation for National Institute of Standards and Technology

IESNA

Abbreviation fro Illuminating Engineering Society of North America

High Intensity Discharge Lamp

Generic term describing mercury vapor, metal halide, high pressure sodium and low pressure sodium light sources and luminaries.

Indirect Glare

Glare Produced from a reflective surface

Discomfort Glare

Glare producing discomfort. This type of glare does not necessarily interfere with visual performance or visibility.

Direct Glare

Glare resulting from high luminance or insufficiently shielded light sources in the field of view

Louver

Grid type of optical assembly used to control light distribution from fixture.

Specular Reflection

Mirror-like reflection

Lamp Lumen Depreciation

Multiplicative factor in calculation of illumination for reduction in the light output of a lamp over a period of time.

Luminaire Dirt Depreciation

Multiplicative factor used in calculation of illuminance for reduced illuminance due to dirt collecting on the luminaries.

Ultraviolet Radiation

Non-visible light can both have harmful and beneficial effects.

Infrared Radiation

Non-visible light characterized by its relation to heat

Luminous Intensity

The luminous flux per unit solid angle in a specific direction from a point source of light. In design, an interior source may be considered a point source if the distance exceeds 5 to 10 times the maximum source dimension of the luminaire. The unit is expressed in candlepower (cp) or candelas or lumens per steradian.

Intensity

The luminous flux per unit solid angle, expressed in lumens per steradian or candela

Luminance

The luminous intensity of any surface in a given direction per unit of projected area of the surface, as viewed from that direction; a directional property of luminous radiations

Reflector

The part of the light fixture that shrouds the lamps and redirects some light emitted from the lamp.

Refraction

The process by which direction of a ray of light changes as the ray passes obliquely from a medium to another

Polarization

The process by which the transverse vibration of light waves are oriented in a specific plane.

Luminous Flux

The rate of flow of light through a surface

Visual Comfort Probability

The rating of a lighting system, expressed as a percent of people who, when viewing from a specified location and in a specified direction

Absorption

The ratio of light absorbed by a material to the light falling upon it.

Reflectance

The ratio of light reflected from a surface to the light incident on the surface.