BS - Lighting

flood

wide beam dispersal pattern

inverse square law

illumination on a surface varies directly with luminous intensity of the source, and inversely with the square of the distance from the source

elliptical reflector (ER)

improved version of R lamps; provide more efficient throw of light by focusing light beam at point slightly in front of lamp before spreading out. used for downlights with deep baffles or small openings (less of light trapped in fixture)

reflector (R) / parabolic aluminized reflector (PAR)

incandescent lamps with reflective coating built into lamp to increase efficiency of lamp and more precise beam control. made with heavier glass; suitable for outdoor use

brightness

incorrectly attributed to luminance, but actually the physiological sensation of the adaptation of the eye

induction lamp

lamp filled with low-pressure mercury vapor. when ionized by high frequency induction coil, mercury vapor produces UV radiation, which strikes a phosphor coating on inside of lamp, producing light. similar process to fluorescent lights except the gas is ionized by an induction coil rather than an electron stream. 48-70 lumen / Watt

sulfur lamps

lamp still in development, uses principle of microwave energy excitation in small globe filled with inert gas and couple mg of sulfur. unlike an induction lamp, no mercury vapor; full-spectrum radiation. 101 lumen / Watt

high pressure sodium (HPS)

lamp that produces light by passing an electric arc through hot sodium vapor. arc tube must be made of ceramic to resist attack by the hot sodium. acceptable color rendition. 55-115 lumen / Watt

fluorescent

lamps containing a mixture of inert gas and low-pressure mercury vapor. when lamp energized, mercury arc formed, creating ultraviolet light (invisible) which strikes phosphor-coated bulb, causing bulb to fluoresce and provide visible light. 35-80 lumen / Watt

high-intensity discharge (HID)

lamps that produce light by discharging electricity through a high-pressure vapor. characterized by high efficacy, rapid warm-up time, rapid restrike time and historically poor color rendering. use when high illuminance is required over large areas and when energy efficiency is desired

mercury vapor

lamps where an electric arc passed through high pressure mercury vapor, causing it to produce blue-green light. 32-63 lumen / Watt

fiber optics

lighting accomplished by bundled fibers; good for recessed ceiling downlights, track / display case lighting in museums, pools. primary advantage = no heat produced where light exits fiber, no UV radiation transmitted

point grid method

lighting calculation method for point sources of light; sum all fixtures in room. only considers direct light, not reflected light

zonal cavity method

lighting calculation method for spaces with several luminaires. takes into account lumen output of lamps, number of lamps, luminaire efficiency, light loss factor

brightness ratios

limited to 3:1 between task and surrounding, 5:1 between task and remote srf, and 10:1 between task and very remote srf

transluscent

material that allows transmittance of light but not of a clear image

2.3 Watts / sf

maximum power that can be consumed in a building for lighting

footcandle

measure of illuminance. 1 fc = 1 lumen/sf

specular reflection

reflection resulting from a smooth, polished surface such as a mirror. the angle of incidence = angle of reflection

diffuse reflection

reflection resulting from a uniformly rough surface, appearing uniformly bright and the image of the source cannot be seen

combined specular and diffuse reflection

reflection that makes surfaces appear brighter at the point where the source is shining than in surrounding areas

luminous intensity

represents the force that generates the light we see; the solid angular flux density in a given direction measured in candlepower

reflectance

the ratio of reflected to incident light falling on a surface

coefficient of utilization

the ratio of useful light arriving at the work plane to the amount of light emitted by the source, which depends on the reflectivity of different surfaces and the aspect ratios of the ceiling, wall, and floor cavities

candlepower

the unit of luminous intensity approx. equal to the horizontal light output from an ordinary wax candle

candlepower (CP)

the unit of luminous intensity, which is the amount of light emitted by a source

lumen

the unit of visible light emitted by a light source, defined as the amount of light passing through one square foot at a distance of one foot from a one candlepower source

luminous flux

time rate flow of perceived luminous energy (flux) emanating from 1 sf of surface area of the implied sphere surrounding the 1 candlepower source with a radius of 1 ft. total flux = 12.57 lumens

tungsten halogen

type of incandescent lamp where there is a small amount of a halogen (such as iodine or bromine) in the bulb with the inert gas. as tungsten filament burns off, mixes with halogen and redeposits back onto filament instead of wall of bulb = longer bulb life, low lumen depreciation. burns under higher pressure and temp than normal incandescent. made of quartz, much smaller. 18-22 lumen / Watt

light-emitting diodes (LED)

very efficient lamp used in a variety of applications. small, low light output, use little power, fast response. 266 lumen / Watt

visible light

visually evaluated radiant energy, form of electromagnetic radiation. wavelengths: 400nm = violet, 70nm = red light

A N S I

American National Standards Institute. (ANSI)

Continuous Spectrum Power Distribution

Sun Incandescent. Halogen incandescent. Light emitting diode. (LED)

Kelvin

5,000 and below is compared to a incandescent light source. 5,000 and above is compared to natural daylight.

Blackbody

An idealized radiator of energy that is at a uniform temperature and whose emitted color spectrum is the maximum that can be emitted by any substance at the same temperature.

Light Loss Factor (LLF)

Area dirtiness Room surface dirt depreciation Lamp percentage burnout Lamp lumen depreciation Luminaire dirt depreciation

Light Pollution

Artificial light entering the night sky and obscuring the stars.

luminous intensity (I)

the amount of light emitted by a source

veiling reflection

a reflection that interferes with viewing task; complex interaction of light source / brightness, position of task / eye, reflectivity of tasks

Halogen Incandescent

Both line voltage and low voltage halogen lamps differ from standard incandescent lamps in that they use an iodine or bromine gas within the bulb to protect against tungsten filament burnout and bulb blackening, which contributes to extended lamp life. 2,600 to 3,200 Kelvin 2,000 to 3,000 hours

Luminance

Brightness of light transmitted by, reflected from, or transmitted through a surface.

Indirect Lighting

Comes from suspended luminaires that radiate 90 to 100 percent of their light upward, where it is reflected around the room. Indirect lighting results in a uniform distribution of light with reduced shadowing and glare.

Ballast

Device providing a controlled electrical current, voltage, and waveform to gas-discharge type lamps.Ballasts provide the energy necessary to start lamp operation, and limit the current that flows through them during operation afterward. Fluorescent and HID lamps.

Illuminance

Density of light on a surface, measured as candela per square foot or footcandles and represented by the symbol E. This is analogous to the gallons of water delivered on a square foot of lawn.

Footcandle Calculation

FC = (number of fixtures x lumens per lamp x lamps per fixture x CU x LLF) / (room square feet) If the desired illuminance level is known and the number of fixture is not, then the term can be rearranged as: (number of fixtures) = (FC x room square feet) / (lamp per fixture x lumens per fixture x CU x LLF)

Direct Lighting

Fixtures radiate 90 to 100 percent of their light down onto the task surface or in the general direction of the surface to be illuminated. Direct lighting is more prone to glare issues, but is more efficient than indirect lighting.

Luminous Flux

Flow of light from a source, measured in lumens. This is analogous to the flow rate of water through a garden hose.

Non Continuous Spectrum Power Distribution

Fluorescent High intensity discharge. (HID) Mercury vapour. (MV) High pressure sodium. (HPS) Low pressure sodium. (LPS)

Fluorescent Lamps

General fluorescent lamps pass a electrical current through an inert and electrically nonconductive gas by first evaporating a small drop of mercury held within the tube each time the lamp is started. The evaporation is accomplished by a high voltage starting current from the fixture ballast. 2,200 to 7,500 Kelvin 6,000 to 30,000 Hours 75 to 90 Lumen per watt (LPW)

High Intensity Discharge Lamps (HID)

High intensity discharge lamp technology includes mercury, metal halide, and sodium gas discharge lamps. In general they have high efficacy and low to average color rendering. Thier most common applications are industrial, commercial, roadways, and security lighting. They all use a ballast to initate and control a flow of electrical current through a gas filled envelope.

High Pressure Sodium Lamps (HPS)

High pressure sodium lamps discharge an arc current through a small ceramic arc tube in the center of the lamp. The arc tube is filled with xenon, sodium, and mercury vapor, but the larger outer bulb volume is drawn down to vacuum pressure. 2,200 to 2,700 Kelvin 10,000 to 40,000 Hours 65 Lumen per watt (LPW) 100 watt 130 Lumen per watt (LPW) 1,000 watt

I E S N A

Illuminating Engineering Society of North America. (IESNA)

Incandescent Lamps

Incandescent lamps generate light by heating a thin tungsten metal filament with electrical current. To prevent oxidation, the filament is sealed in a bulb of inert gas. 2,750 to 3,200 Kelvin 750 to 1,500 Hours Very inexpensive, easy to replace. Measured in 1/8"

Types of Lamps

Incandescent. Halogen incandescent. Fluorescent High intensity discharge. (HID) Mercury vapour. (MV) High pressure sodium. (HPS) Low pressure sodium. (LPS) Induction. Light emitting diode. (LED)

Induction Lamps

Induction lamps resemble general service incandescent A lamps, but operate like gas discharge lamps. At the center of the lamp itself is an induction coil, which produces a magnetic field and excites a mercury electron ion plasma material on an inner glass assembly, producing ultraviolet light. 3,000 to 4,000 Kelvin 10,000 to 60,000 Hours 75 Lumen per watt (LPW)

C I E

International Commission on Illumination. (CIE)

Task Light

Is provided by direct point to point illumination from a fixture or fixtures onto a single point on a surface such as a desk.

Brightness Ratio

Is the relationship between the illumination levels of the surfaces within a person's field of vision. The maximum ideal brightness level ratio between a task and the adjacent surroundings should be under 1:1/3

Ambient Light

Is the uniform level of illuminance provided in a room from a uniformly spaced grid of fixtures.

Correlated Color Temperature (CCT)

It is the measure of the color coming from the light source. This is the absolute temperature in degrees Kelvin required for a blackbody to radiate a color spectrum most similar to that of a given light source. Reds being warm, blues being cool.

Light Emitting Diode Lamps (LED)

Light emitting diode use semiconductor diode lamps. 10 years 32 Lumen per watt (LPW)

Luminaire

Lighting fixture including housing, lamp, ballast, lens, reflector, and louvers or baffles. Some of these components are optional or may be part of the lamp.

Lamp

Lighting source used in a fixture to generate visible energy. Many fixtures use more than one lamp.

Low Pressure Sodium Lamps (LPS)

Low pressure sodium lamps have a very high efficacy, they have no color rendering capability due to their strictly monochromatic light with very low color rendering index. 2,000 Kelvin 16,000 to 18,000 Hours 100 to 150 Lumen per watt (LPW)

Efficacy

Lumens of light output for each watt of electricity consumed. This is a measure of how efficient a lamp is, but not necessarily how efficient a light system will be. Lumens per watt (LPW)

Unrecoverable light Loss Factor

Luminaire ambient temperature Luminaire voltage Ballast efficiency factor Luminaire surface depreciation

Color Rendering Index (CRI)

Measure of the color shift in the appearance of objects when lit by a light source, as compared to being lit by a reference light source of the same color temperature. C R I is measured in percentage, with higher numbers being closer to color rendering of the reference light source. 0 to 60 poor, 60 to 80 okay, 80 to 90 good, 90 to 100 excellent

Metal Halide Lamps (MH)

Metal Halide lamps were developed from mercury vapor lamp technology by the addition of metal halides to the mercury and argon in the arc tube. 2,500 to 5,000 Kelvin 15,000 to 30,000 Hours 75 to 125 Lumen per watt (LPW)

N E M A

National Electrical Manufacturer Association. (NEMA)

Luminous Intensity

Radiant energy emitted by a source, measured in candela and represented with the symbol L. This is analogous to water pressure in a hose.

Light Power Density (LPD)

Ratio of watt per square foot. Or alternately called Unit Power Density (UPD), or Lighting Power Allowance (LPA). Allowable Light Power Density under model code is dependent on the building type, occupancy, or area use category.

direct glare

glare that results from a light source in field of vision causing discomfort and interference with with visual task. extent of problem depends on source, its position, background light, adaptation of the eye

compact fluorescent (CF)

fluorescent lamp that has either T-4 or T-5 glass envelope bent into U or double U mounted on special base that houses the ballast and allows the lamp to be screwed into existing incandescent luminaires 55-75 lumen / Watt

rapid start lamps

fluorescent lamp that maintains a constant low current in cathode which allows them to start within 2 seconds. have supplanted preheat lamps

instant-start lamps

fluorescent lamp that uses a voltage high enough to start the arc in the tube directly without pre-heating the cathode

Mercury Vapor Lamps (MV)

Suitable for outdoor applications, blue and green spectrum. Not to be used indoors because of the poor skin lighting. 3,200 to 6,700 Kelvin 10,000 to 24,000 Hours 25 to 32 Lumen per watt (LPW) for small lamps 100 watts 50 to 60 Lumen per watt (LPW) for large lamps 1,000 watts

reflected glare

glare that occurs when a light source is reflected form a viewed surface into the eye

Candlepower Distribution Curve (CDC)

The candle distribution curve is a polar coordinate plot graphically showing the candela output from a fixture at any angle relative to one fixture axis. It also indicates the cutoff angle or shielding angle, above which no light is emitted.

Illumination

The common term for footcandles of illuminance, but also used in a more general sense to describe the means of lighting a space. For clarity, when used to refer to footcandle levels, the term illumination is preferred.

Coefficient of Utilization (CU)

The fixture efficiency. C U can usually be assumed in the range of 0.5 to 0.8

Bulb or Tube

The glass envelope of a lamp

Light Trespass

Unwanted artificial light falling onto an adjacent property.

Class A ballast

a ballast appropriate for spaces with low ambient noise levels

electronic ballast

a ballast developed to meet more stringent energy conservation requirements. produces high frequency AC (25-30kHz). reduces flicker, noise, power consumption and easier to dim

Class F ballast

a ballast suitable only for noisy environments

luminaire

a complete light fixture, including lamps

ballast

a device in all fluorescent lamps that supplies the proper starting / operating voltages to lamp and limits the current (typ 60kHz) produce noise and heat

starter

a device which starts the arc in a neon or fluorescent lamp, or a contactor and overload relay used in starting some electric motors

isolux (footcandle) chart

a diagram showing lines of equal illumination produced by a specific luminaire from a specific manufacturer. produced by full-scale mockups or computer simulation

luminaire dirt depreciation (DDF)

a factor that represents light loss due to accumulated dirt

lumen depreciation (LLD)

a factor that represents light loss with age

high-intensity discharge (HID)

a family of lamps consisting of quartz envelope inside a glass envelope. in the quartz envelope, the current causes an intense arc between two electrodes, exciting a plasma of mercury, metal halide, or high-pressure sodium and producing visible light

light loss factor (LLF)

a fraction that represents amount of light lost due to lumen depreciation, luminaire dirt depreciation, lamp burnout, surface direct, operating voltage of lamps, operating temperature

tochere

a freestanding light fixture that directs most of its output to the ceiling

incandescent

a lamp that consists of a tungsten filament placed within a sealed bulb containing inert gas. when electricity passed through lamp, filament flows, producing light. 8-22 lumen /W

footlambert

a measure of luminance, the luminous flux per unit area leaving a surface

lumen

a measure of photometric power. the unit of luminous flux equal to the flux from a uniform point source 1 ft away of 1 candlepower on a sphere. 1 lumen = candlepower/12.57

metal halide

a modified mercury vapor lamp, but smaller and with better color rendition due to addition of thallium, indium, and sodium halides to arc tube. 80-125 lumen / Watt

color temperature (K)

a single number rating of a light source based on their dominant color. low temperatures (3100K) = warm colors. high temperatures (5000K) = cool colors

task ambient

an approach to lighting design that recognizes it is inefficient to illuminate an entire room to level require for individual tasks. rather, provide general background illumination and separate light fixtures at individual workstations.

ballast

an electrical device used with fluorescent and other lamps to provide starting voltage and regulate current flow through the lamp

preheat lamps

an old technology for fluorescent fixtures where the gas is preheated. uses a seperate starter. might be present in order fluorescent fixtures, but not used in new types

light sources sorted by efficacy - low to high

candle incandescent tungsten-halogen fluorescent compact fluorescent mercury-vapor metal-hallide high-pressure sodium induction sulfur LED daylight

rods

cells around the edges of the retina, extremely sensitive to light and motion. not great at discriminating color or detail

cones

cells located near the central portion of retina; extremely sensitive to detail / color. only 2 degree cone of vision around line of sight

spectral energy distribution

characteristic of every lamp; measure of energy output at different wavelengths or colors

45 degrees from light source

critical angle for direct glare. solve problem by using luminaire with 45 degree cutoff angle

daylight factor method

daylighting calculation method developed in Europe assumes overcast or diffuse sky conditions. sanctioned by CIE, often used in computer programs. can calculate daylight in any location in the room. the result is a number that expresses the amount of light at a particular interior location as a percentage of light AVAILABLE on an exterior horizontal surface

visual comfort probability (VCP) factor

factor developed to evaluate direct glare. equals percentage of normal observers experiencing visual comfort in particular environment / lighting condition

lumen (flux) method

method for calculating daylighting developed in the US, suited to both clear and partly cloudy skies. amount of daylight calculated in 3 locations: 5ft from window, middle of room, 5ft from back of room. CANNOT be used for room with corner windows

1 fc

minimum lighting level at the floor for emergency lighting

low pressure sodium (SOX)

most efficient / economical lamp, but only produces monochromatic yellow light. used for street / security lighting 55-115 lumen / Watt including ballast loss

color rendering index (CRI)

rating of a light source comparing the perceived colors of an object as compared with daylight. max rating = 100. a rating of 85 or more is considered good

coefficient of utilization (CU)

rating of a luminaire that represents the fact that not all of the lumens produced reach the work surface. ranges from 0.01 to 1.00 (most values 0.5 - 0.8), depending on design of fixture and condition of room

efficacy

ratio of luminous flux emitted to total power input. measured in lumens per watt. important measure of energy efficiency of light source

efficacy

ratio of the lumens emitted by a lamp to the electrical power consumed by the lamp

reflectance / reflectance coefficient

ratio of total reflected light to total incident light, expressed as a percentage

transmittance / coefficient of transmission

ratio of total transmitted light to the total incident light, expressed as a percentage

low voltage miniature reflector (MR)

small tungsten-halogen lamps available in wide variety of wattages and beam spread. regenerative halogen cycle provides consistently high output. whiter than standard incandescent lamps

Illuminating Engineering Society (IES)

society that publishes recommended lighting levels for various tasks, determines maximum amount of power used for lighting for a particular building type

narrow

spot beam dispersal patten

CIE sky

standard overcast sky developed by Commission Internationale de l'Eclairage. the sky has a nonuniform brightness distribution, increasing from horizon to zenith in a 1:3 ratio. with an overcast sky, exterior horizontal illuminance varies directly with sun's altitude, irrespective of azimuth

footcandle

the basic unit of illumination arriving at a work plane. one footcandle is equal to one lumen per square foot

illuminance

the density of luminous flux incident on 1 sf of surface. measured in footcandles

contrast

the difference in illumination level between one point and nearby points

illumination

the intensity of light falling on a surface, usually expressed in footcandles

wavelength

the length of one complete cycle or waveform, for light or sound waves. in light, the dominant wavelength determines the perceived color

luminance

the luminous flux per unit of project area leaving a surface, measured in footlambert. takes into account the reflectance and transmittance properties of materials and directions they are viewed. sometimes incorrectly referred to as "brightness", but in reality is measurable state of object luminosity