A.V.4. Illumination

Lumen Method (Flux Method) (Zonal Cavity Method)

A procedure in lighting design used to determine the number and types of lamps or luminated 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 a 0.9 or higher rated power factor, which is achieved by using a capacitor

Normal Power Factor

A ballast/lamp combination in w/c no components have been added to correct the power factor, making it normal

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.

Light

An artificial source of illumination, electromagnetic radiation that the unaided human eye can ppercieve.

Incandescence

As an element is heated, its molecules become increasingly active until the temperature of the element reaches about 500 deg. C, only heat radiation is released.

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 light output from a source, primarily by bending the waves of light.

Light Loss Factor

A factor used on calculating illuminance after a given period and under given conditions. Also known as Maintenance factor.

Instant Start

A fluorescent circuit that ignites the lamp instantly with a very high starting voltage from the ballast. It has single-pin bases.

Lay-in Troffer

A fluorescent fixture, usually a 2'x4' fixture that sets or "lays" into a specific ceiling grid

Phosphorescence

Describes the action of organic flourescent material which retains the radiant energy for short period of time

Tungsen Halogen Lamp

A gas filled tungsen filament incandescent lamp with a lamp envelope made of quartz to withstand the high temperature. This lamp contains some halogens which slow the evaporation of the tungsen. Also common called as "quartz lamp"

High Pressure Sodium Lamp

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

High Output

A lamp or ballast designed to operate at higher current and produce more light.

Low - Voltage Lamp

A lamp typically compact halogen that provides both intensity and good color rendition. Lamp operated at 12V and requires the use of a transformer.

Fluorescent Lamp

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

Low Pressure Sodium

A low pressure discharge lamp in w/c light is produced by radiation from sodium vapor. Considered a monochromatic light source

MR-16

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

Fluorescence

A means of producing light from gaseous discharge. In this case, the confined gas is one which produces a relatively high percentage of ultraviolet light. The confining glass tube is coated with phosphor crystals which absorbs and convert UV radiation into longer wavelength in the visible spectrum

Luminous Efficacy

A measure of the effective with w/c a light source converts electric power into luminous flux

Efficacy

A metric used to compare light output to energy consumption. It is measure in lumens per watt. It is similar to efficacy, but is expresed in dissimilar units.

Room Cavity Ratio (RCR)

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

PAR Lamp

A parabolic aluminized reflector lamp. An incandescent metal halide or compact fluorescent lamp used to redirect light from source using a parabolic reflector. Lamp are available with flood or spot distributions

Constant Wattage Autotransformer (CWA) Ballast

A popular type of HID ballast in w/c the primary and secondary coils are electrically connected. Considered an appropriate balance between cost and performance

Constant Wattage Ballast

A premium types of HID ballast in w/c the primary and secondary coils are isolated. It is considered a high performance.

Valence Electrons

One of the electrons in the outermost shell of an atom

High Bay

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

Kinds of Luminescence

Photoluminescence Gaseous Discharge Flourescence Phosphorescence Electroluminescence

Footcandle FC

The English unit of illumination equal to 1 lumen per square foot; light flux density

Critical Angle

The angle at which light undergoes total internal reflection

Beam Angle

The angle between two directions for w/c the intensity is 50% of the max. intensity, as measured in a plane through the nominal beam center line.

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: ROYGBIV

Electroluminescence

The conversion of electric energy to light using the passage of alternating or direct current through special conductors of solid matter producing visible light.

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 in brightness between an object and its bakcground

Luminescence

The emmision of light not directly ascribable to incandescence

Work Plane

The level at which work is done and at which illuminance is specified and measured. For office applications, this is typically a horizontal plane 30 in. above the floor (desk height)

Illumination

The luminous flux density incident on a surface

Luminosity

The ratio of luminous flux to the corresponding 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.

Reflectance

The ratio of reflected light to incident light

Coefficient of Utilization (CU)

The ratio of the luminous flux from a laminate, calculated as recieved on the work place to the luminous flux emitted by the luminaire's lamp.

Absorptance

The ration of light absorbed by a material to the light falling upon

Luminance Contrast

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

Glare

The sensation produced by luminance within the visual field that is sufficiently greater than the luminance to which the eyes are adapted. It may cause annoyance, doscomfort or loss of visual performance or visibility

Recessed

The term used to describe the doorframe 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 characteristics of light passing through it. Usually made of glass or acrylic

Diffuse transmission

Upon translucent material, however, such as plastic, the emerging light will spread in all directions.

Luminescence

When an electric current is introduced through a gas or solid which is composed of a single valence electron. It cause the valence electrons to temporarily rise to a higher level of energy. When the electron resumes its natural state, it radiates energy in the form of light.

Specular Reflection

When the material has a polished surface, the light will be reflected at an angle equal to the angle of incidence

Diffuse Reflection

When the material has an unpolished surface, however, the reflected light is spread in all diredction by multiple reflection on the unpolished surface

Diffusion

When the reflected light rays are distributed in all direction with max. intensity normal to the surface

Infrared Radiation

It is a non-visible light characterized by its relation to heat

Ultraviolet Light

It is a non-visible light that can have both harmful and beneficial effects

Energy of Light

It is a small band of wavelength in the electromagnetic spectrum which ranges from radio frequencies to cosmic rays

Light

It is an artificial source of illumination. It is determined by wavelength with red having the longest wavelength, violet being the shortest.

CCLFLFL (Candela Candle Power Lux Footcandle Lamber Footlambert Lumen)

Lighting and Illumination units

T12 (Lamp)

Industry standard for a fluorescent lamp that is 12 1/8 (1 in) in diameter.

Compact Fluorescent

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

Point Source

A source of essentially zero dimension that radiates light uniformly in all directions.

Color Temperature

A specification of the color apperance of a light source, relation the color to reference source heated to a particular temperature, measured by the thermal unit: Kelvin.

Metal Halide

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

Mercury Vapor Lamp

A type of high-intensity dischage (HID) lamp in which most of the light is produced by radiation from mercury vapor. Emits blue-green cast of light. Available in clear and Phospho-coated lamps

Lux

A unit of illumination equal to 1 lumen per square meter

Lambert

A unit of luminance equal to 1/pi candela per square cm.

Footlambert (FL)

A unit of luminance equal to 1/pi candela per square foot.

Lumen

A unit of luminous flux

Candela

A unit of luminous intensity, describing the intensity of a light source in a specific direction

Luminance Meter (Brightness Factor)

A visual instrument or photoelectric instrument used to measure luminance

LED

Abb. for LIGHT EMITTING DIODE. an illumination technology used for exit signs. Consumes low wattage and has a rated life of greater than 80 years

NIST

Abb. for Nation Institute of Standards and Techonology

NEMA

Abb. for National Electrical Manufacturers Assocation

IESNA

Abbreviation for : Illuminating Engineering Society of Nort America

ARTDRP (Absorption Reflection Transmission Diffusion Refraction polarization)

Fundamental Laws of Light

High Intensity Discharge (HID) Lamp

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

Indirect Glare

Glare produced from a reflective surface

Discomfort Glare

Glare producing discomfort. This type of glare does not necessarily interfere with visual perforamance 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 characteristics of light distribution from a fixture.

Lamp Lumen Depreciation

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

Luminaire Dirt Depreciation (LDD)

Multiplicative factor used in calculations of illuminance for reduced illuminance due to dirt collecting on the luminaires.

Types of Visible Light Sources

Natural Phenomena Incandescence Temperature Radiation Luminescence (Types of Visible Light Sources)

Infrared Radiation

Non-visible light characterized by its relation to heat

Natural Phenomena

Radiation of the complete spectrum of light from the sun or stars; the reflection of sunlight off the moon; sky,clouds,etc.

Reflectance

Ratio of reflected to incident light

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 5-10 times the maximum source converts electric power into luminous flux.

Intensity

The luminous flux per unit solid angle, expressed in lumens per steradian (lm/sr) or candela

Candle Power

The luminous intensity of a light source, expressed in candelas

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 radiation

Reflector

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

Polarization

The phenomenon wherein the waves vibrates only in one plane

Photoluminescence Gaseous Discharge

The principle which describes the response of single valence of electrons when their atoms are in a gaseous state. The collision of electrons induced by the introduction of electrical current within a confined gas generates an arc discharge, ionizing the vapor molecules.

Refraction

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

Refraction

The property of a material to change direction of light at the interface between two different materials, such as air and glass

Luminous flux

The rate flow of light through a distance

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. They are often used for lighting calculations.

Luminaire Efficiency

The ratio of luminous flux emitted by a luminaire to a total flux emitted by the lamp or lamps in the luminaire