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Training for Jabatan Warisan negara Malaysia. Basic Lighting System Student Notes

Training for Jabatan Warisan negara Malaysia. Basic Lighting System Student Notes

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  • 1. FIRESPEC ENGINEERING (M) SDN BHD Industrial Standard and Glossary Lighting Design Hj Azlan Abass 11/7/2011Proprietary and Confidential Information
  • 2. 1|PageContentsBasic Lighting Knowledge .................................................................................................. 21). Lumen(lm) .................................................................................................................. 22). Candela(cd) ................................................................................................................. 23). Beam Angle [Unit:degree] ........................................................................................... 24). LUX(lx) ........................................................................................................................ 35). Color Temperature / Correlated Color Temperature(CCT) ........................................ 36). Color Rendering Index(CR) ........................................................................................ 37). Efficacy(lm/W) ........................................................................................................... 48). Design Life Time ........................................................................................................ 49). Dimmability ............................................................................................................... 4Why LED Lighting Solution ?............................................................................................. 5Industry Standards and Glossary ...................................................................................... 6 LumaStream embraces the industry standards evolving on both federal and state levels. ........................................................................................................................... 6Lumen Method Calculations ............................................................................................ 29Firespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 3. 2|PageBasic Lighting Knowledge1). Lumen(lm)Lumen is the international (SL) unit of luminous flux, a measure of overall light emitted by a lightsource.2). Candela(cd)Candela is the international(sl) unit of luminuous intensity,a measure of light emitted by a light sourcein a particular direction.Any given light source will have different luminous intensities in different directions considered.[candela = lumen/solid angle]3). Beam Angle [Unit:degree]Beam angle is the angle between two directions for which the luminous intensity is 50% of themaxmum intensity as measured in a plan through the nominal beam centerline.Beam angle of a bulbgives an idea of how the light beam spreads away from the beam center.Firespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 4. 3|Page4). LUX(lx)Lux is the international(SL)unit of illuminance, a measure of light arriving at a surface, 1 lumen persquare foot equals 1 footcandle, while 1 lumen per square meter equals 1 lux .[lux = lumen/m2]5). Color Temperature / Correlated Color Temperature(CCT)A black-Body radiator will have a different color whent it is heated up to different temperatures(inkevin).The Temperature at which the heated black-body radiator matches the color of the light sourceis the color temperature of the light source.6). Color Rendering Index(CR)Color rendering index ranges from 0-100 ,measures a light sources ability to reproduce the color ofvarious objects being lit by a reference light source, black body radiator(CRI=100)Firespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 5. 4|Page7). Efficacy(lm/W)Eifficacy is the effciency of a light source to concert electricity energy to light energy which is expressedin lumen output per unit power input (watt)[Efficacy = lumen / wattage]8). Design Life TimeDesign life time is the average life of a lighting product when it is operated at nominal lampvoltage,current and controlled working environment. Actual lamp life varies because of any differentfrom those rating condition.9). DimmabilityNot all lighting prodcuts is designed for dimming function. Dimming a non-dimmable LED lightingproduct will cause un-predictable result and may affect the life time of the products.The below figureshows the typical input current variation while adjusting the DC voltage input to dimmable and non-dimmable product.Firespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 6. 5|PageWhy LED Lighting Solution ?Technology is changing lives at a pace never before witnessed in all of human history, andwith it, the way we see the world. More than a hundred years ago the incandescent filamentbrought illumination to the night, multiplying human productivity at an exponential rate.Later, fluorescent light rose up as a power-saving alternative to the incandescent.And now there is a new source of light, once again on the cusp of transformational change -OPTILED has seen the future, and it will no doubt be lit by Light Emitting Diodes, morecommonly known as LED. A low-power, high-efficiency technology created with non-toxicmaterials, LED lamps are the next generation of lighting, leading the way into the green ageof illumination. Because LED lighting by OPTILED is safe, long-lasting and increasinglycost-effective, it will play an important role in creating a more environmentally sustainablefuture for many years to come.OPTILED has touted the benefits of LED since long before it became cool to do so andcontinues to work hard to change perceptions of LED technology. LED is no longer just aniche product, and we have the expertise, technical knowhow, R&D and the people neededto create the best general functional LED lighting solutions on the market.There are a number of important reasons why OPTILED LED lighting is better than otherlighting technologies: Longer life spans: OPTILED LED lamps last 35,000 hours - 30 times longer thanincandescent, 25 times longer than halogen and 10 times longer than compact fluorescentlamps. Not only will you be helping the environment, youll be saving money, too. High Efficiency: Saves users up to 70% on energy usage compared to standard dichroiclow-wattage halogen and incandescent lamps, lowering electricity bills. An 5W LED MR16bulb generates as much light as an 9W CFL, an 35W halogen, and 80% energy savingcompared to CFL downlight - A 15W LED downlight generates as much light as a 2x13WCFL downlight and 75W incandescent bulb. Energy usage translates directly into significantcost savings, especially in commercial applications where large quantities of lamps areused. Green lighting technology: Lower energy usage makes LED lighting better for theenvironment, but its a very green technology in other ways as well. Since no heat isproduced, it can reduce interior temperatures by 1-2 degrees, lowering air-conditioningcosts and CO2 emissions. LED lighting is also much safer for the environment because it ismercury-free and doesnt produce IR or UV rays, which can be harmful to humans. In otherwords, LED lamps are the greenest and most environmentally-friendly source of light on themarket. Superior color, increased comfort: Clear light and high marks on the Color RenderingIndex (CRI), which indicates accurate true color reproduction, means LED lights producelight that is more pleasing and relaxing, increasing comfort and mood.Firespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 7. 6|PageIndustry Standards and GlossaryLike traditional lighting products, LED-based luminaires sold in the US are subject toindustry standards governing safety and performance. To accommodate LEDs, someexisting standards and test procedures are being modified and new standards have beendeveloped.LumaStream embraces the industry standards evolving on both federal and statelevels.Within this rapidly evolving industry, the "language" for certain concepts, components,systems, applications, etc. is not well established and consistent throughout the industry.This fact has created confusion between vendors, engineers, consumers, manufacturers,and others. LumaStream believes it is important to define the language we use within ourcompany and throughout our website. As naming conventions become standardized we willupdate these definitions.Binning and labelingis the process of separating LEDs based on their various characteristics and assigning themwith a specific bin code. LEDs with the same characteristics are placed on a reel. WhiteLEDs are sorted by color and brightness. Color LEDs are sorted by dominant wavelengthand brightness. LumaStream relies on Philips, an industry partner, for precise binningspecs of the Philips Rebel chip.CALiPERis Department of Energys (DOE) SSL Commercially Available LED Product Evaluation andReporting (CALiPER) program. CALiPER independently tests and provides unbiasedinformation on the performance of commercially available SSL products. Working in thepublics interest, the DOE publishes test reports, technical information, and summaries ofmanufacturers products and is intended solely for the benefit of the public, in order to helpbuyers, specifiers, testing laboratories, energy experts and others make informed decisionsabout SSL products and related technologies.CALiPER ProgramDepartment of Energys (DOE) SSL Commercially Available LED Product Evaluation andReporting (CALiPER) program independently tests and provides unbiased information onthe performance of commercially available SSL products. Working in the public interest, theDOE publishes test reports, technical information, and summaries of manufacturersproducts and is intended solely for the benefit of the public, in order to help buyers,specifiers, testing laboratories, energy experts and others make informed decisions aboutSSL products and related technologies. Manufacturers products are selected randomly forCALiPER program testing.CALiPERs main tests measure and assess (1) energy efficiency of SSL products, as specifiedin IES LM-79 under luminaire efficacy, via this formula: Total lumens emitted by theluminaire, divided by the total watts drawn by the luminaires power supply; (2) thermalmanagement and the effect of temperature on lumen depreciation.Firespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 8. 7|PageCorrelated Color Temperature (CCT)is the measure used to describe the relative color appearance of a white light source. CCTindicates whether a light source appears more yellow/gold/orange or more blue, in terms ofthe range of available shades of "white." CCT is measured in degrees Kelvin (unit of absolutetemperature). Cool White targets a typical CCT between 10,000K and 4500K; Neutral White,between 4,500K and 3,500K; Warm White, between 3,500K and 2,540K.Color Rendering Index (CRI)indicates how well a light source renders colors of people and objects, compared to areference source of like color temperature.Integrationis the "marrying" of lighting and lighting control components. Integration can set properlight levels and atmosphere for office video-conferencing, or create comfortable dynamicscenes within a residential setting.Interfaceis the human mechanism for interacting with the lighting system; typically consisting of acomputer or a wall mounted control panel.LED Light Engineis a subsystem of an LED luminaire that includes one or more LED packages, an LEDarray, or an LED module; an LED driver, electrical and mechanical interfaces; and anintegral heat sink to provide thermal dissipation. An LED light engine may be designed toaccept additional components that provide additional aesthetic, optical, and environmentalcontrols. An LED light engine is designed to connect to the branch circuit.LM-79IESNA approved method for the electrical and photometric measurements of SSL. LM-79specifies procedures for measuring total luminous flux, electrical power, luminous efficacy,and chromaticity of SSL luminaires and replacement lamp products.LM-80IESNA approved method for measuring lumen maintenance of LED light sources. LM-80specifies procedures for determining lumen maintenance of LEDs and LED modules (butnot luminaires) related to effective useful life of the product.Lumen depreciationis the decrease in lumen output that occurs as a lamp is operated. For most light sources,the lamp fails before significant lumen depreciation occurs; for example, a typicalincandescent bulbs lumen output will only decrease 10-15% over 1,000 hours of use, butthe bulb will fail at this time.* Because LEDs will continue to operate at very low lightFirespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 9. 8|Pagelevels, LED life is usually defined as lumen depreciation to a particular point, such as 70%of initial lumensLuminous efficacyis the most commonly used measure of the energy efficiency of a light source. It is stated inlumens per watt (lm/w), indicating the amount of light a light source produces for each wattof electricity consumed.NEMA SSL-1 Power SupplyNational Electrical Manufacturers Association (NEMA) standard that specifies operationalcharacteristics and electrical safety of SSL power supplies and drivers.Retrofitmeans to substitute new or modernized systems for older lighting equipment. LumaStreamdesign-build systems can incorporate partial or complete retrofit and upgrade solutions.Scalabilityis a desirable property and benefit of a solid-state lighting system whereby capabilities canbe put in place to successfully accommodate future lighting needs. LumaStream systemsallow for expanding lighting needs and system control.Scalable Systemis a system designed to accommodate scalability, i.e. it can grow as the clients lighting orcontrol needs grow and change. LumaStream specializes in identifying whether our clientssystems need to be designed to accommodate scalability.Solid-State Lighting (SSL)refers to a type of lighting that uses light-emitting diodes (LEDs) as its source ofillumination.TM-21Lumen Depreciation Lifetime Estimation Method for LED Light Sources. TM-21 will providea method for determining an LED luminaire or integral replacement lamps expectedoperating life, based on initial performance data collected per IES-LM-80.UL1598/8750AUL standard for Luminaires - specifies the minimum safety requirements for luminaires.The requirements in this document may be referenced in other documents such as UL8750or separately used as part of the requirements for SSL products.Firespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 10. 9|PageUL1310/8750UL standard for Class 2 Power Units - specifies the minimum safety requirements for Class2 power supplies. (as defined by the National Fire Protection Association (NFPA), 70-2005)UL-8750Underwriters Laboratory (UL) has developed this safety standard for "Light Emitting Diode(LED) Light Sources for Use in Lighting Products." Currently, UL has in place an "Outline ofInvestigation" that references all existing UL standards applicable to LED lighting products.The purpose of the outline is to provide a comprehensive approach and listing of applicablestandards for UL treatment of lighting products based on LEDs. The outline will be useduntil the full LED specific document is completed.White Lightcomprises light from all the frequency bands in the visible spectral range. Hence, it is acombination of red, orange, yellow, green, blue, indigo, and violet.Firespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 11. 10 | P a g eAchromaticDescribing the property of having no colour (or hue). For example a neutral white, grey orblack colour.Additive Primary ColourThe additive primary colours are Red, Green & Blue. When equal amounts of light of thethree additive primary colours is combined, white light is generated. Combining two additiveprimaries in equal amounts creates a subtractive primary colour. See also: SubtractivePrimary Colour.Angstrøm (Å)A unit of wavelength of light. One Angstrøm (Å) is 0.1nm (or 1 x 10 -10 m).Average (Luminous) IntensityApplies to LEDs. The near-field luminous intensity for a non point source. Defined in CIEdocument 127 as being the intensity (luminous flux per unit solid angle) measured by aphotodetector with an input area of 100 mm2 positioned at either 316mm (condition A) or100mm (condition B) from the tip of the LED source, measured on the mechanical axis ofthe LED. Average luminous intensity has units of candela (cd). Not to be confused withluminous intensity which is a far-field measurement of the luminous flux per unit solidangle from a light source. See also: LED; Luminous Intensity; Luminous Flux; CIE; Far-Field; Near-FieldBandwidthSee Linewidth.Barium SulphateA white pigment commonly used to coat the interior of integrating spheres and otherreflecting chambers. Exhibits diffuse reflectance. Forms the basis of the following Labspherediffuse relfectance coatings: Spectraflect; Duraflect; and 6080.BlackThe (near) complete absorption of light as a result of no (low) reflectance. In colorimetry,describes a colour of low saturation and low luminance.Blackbody RadiationRadiation that is full or complete, containing all wavelengths. The spectral powerdistribution of light emitted from a blackbody is a function of its temperature only and isdescribed by Planck‟s law. See also: Colour Temperature.Blackbody RadiatorA source that emits blackbody radiation.Firespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 12. 11 | P a g eBrightnessThat attribute of visual perception that describes the degree to which an object emits orreflects light. In colorimetry, brightness is used in the HSB colour model – Hue, Saturationand Brightness. Describes the lightness of the colour, on a scale ranging from black towhite. Can be confused with saturation hence its use is discouraged. Can also be usedinstead of luminance – again its use is not recommended. See also: Luminance.Candela (cd)The SI base unit used in photometry. The candela is the unit of luminous intensity. Thecandela is one of the seven base units of the SI system. Since 1979, the candela has beendefined as: “the luminous intensity, in a given direction, of a source that emitsmonochromatic radiation of frequency 540 x 10 12 Hertz and has a radiant intensity in thatdirection of 1/683 Watts per steradian” (where the steradian is the unit of solid angle). Onecandela equals one lumen per steradian. See also: Luminous Intensity; Steradian.Candela per Square Meter (cd/m2)The SI unit of luminance. One cd/m 2 equals one lumen per square meter per steradian. Seealso: Luminance; Steradian.Candle PowerThe luminous intensity of a light source having units of candelas.CCDAcronym. Stands for Charge Coupled Device. A monolithic, two-dimensional semiconductor(silicon-based) detector array. When illuminated by optical radiation in the range betweenapproximately 300 and 1100nm, produces a photocurrent, the magnitude of which isproportional to the level of light received. Each detector in the array is called a pixel.CFLAcronym. Stands for Compact Fluorescent Lamp.ChromaThe lightness of a colour. Denotes the degree of lightness or darkness. See also: Lightness.ChromaticDescribed as having colour (or hue) – not white, grey or black.ChromaticityIn colorimetry, describes the intensity or level of saturation of a colour (hue), defined as thedistance in the particular colour space of a colour from the neutral grey colour with thesame value.Firespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 13. 12 | P a g eChromaticity Coordinates (CIE)A numeric descriptor of colour. Defined as the ratio of the three tristimulus values XYZ inrelation to the sum of the three, designated by xyz respectively. It is normal to assume thatthe chromaticity coordinates refer to the CIE 2° observer (1931). For reflected colour, it isassumed to be calculated for standard illuminant C unless specified differently. See also:(CIE) x, y; (CIE) u‟, v‟.Chromaticity DiagramThe two-dimensional graph which plots the chromaticity coordinates. For the CIE 2°observer (1931), x is plotted as the abscissa, y as the ordinate. The colour space plots thespectrum locus of monochromatic radiation in the spectral range 380-770nm.CIEAcronym. From the French name "Commission Internationale de Léclairage". In Englishthis is the International Commission on Illumination. CIE sets the standards and providesa worldwide forum for the exchange of information on the science of light, lighting, colourand vision. Click here to visit the CIEs web siteCIE 1976 L*u*v* Colour SpaceA uniform colour space adopted by CIE in 1976 that is used when measuring colour as aresult of additive mixing from emitters of light.CIELABA uniform colour space adopted by CIE in 1976 within which L*a*b* colour coordinates areplotted using a Cartesian coordinate system. This colour space plots equal colourdifferences at approximately equal distances. The L* value denotes the lightness, a*represents the red/green axis, while b* represents the yellow/blue axis. CIELAB is thatcolour space used in relation to the measurement of reflected or transmitted colour.CIE Luminosity Function (Y)See: Photopic Response.CIE Standard IlluminantStandard light source spectral power distributions as defined by CIE for several types oflight source. See Illuminant A, B, C, D, E & F.CIE Standard Observer FunctionSee: Photopic Response; Scotopic Response; Tristmulus Response.CMYKAcronym. Stands for Cyan, Magenta, Yellow & blacK. See also: Subtractive Primary Colour.Firespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 14. 13 | P a g eColorimeterAn instrument that measures the colour of the light it receives. Applies to instruments thatmeasure reflected (transmitted) light as well as to those that analyse the light emitted by asource. Applies to instruments that use RGB optical filters to mimic the tristimulus colourresponse of the human eye. See also: Tristimulus.ColorimetryThe science of measuring the colour of light (emitted, reflected or transmitted) from anobject with a spectral response matching that of the human eye. See also: Tristimulus.ColourCan be described as being one aspect of an object‟s appearance. In colorimetry, colour is avisual perception and is defined in respect of its hue, saturation and lightness.Colour DifferenceBeing the size of the difference between two colours in a defined colour space.Colour Rendering Index (CRI)A metric which defines how well colours are rendered by different sources of illuminationcompared to a defined standard illuminant. There are fourteen special colour renderingindices (Ri where i = 1-14) which define the colour rendering of the light source when usedto illuminate standard colours. The general colour rendering index (Ra) is the average of thefirst eight special colour rendering indices (which correspond to non-saturated colours).Colour SpaceThe three-dimensional solid enclosing all possible colours. The dimensions of the colourspace can be described in a number of different geometries, which leads to various spacingswithin the colour space.Colour SpecificationBeing the tristimulus values, chromaticity coordinates and luminance value (or other colourscale) that are used to uniquely describe a colour numerically.Colour TemperatureColour temperature defines the colour of radiation emitted from a perfect blackbodyradiator held at a particular temperature. Colour temperature is reported in units of Kelvin(K). The plot of the chromaticity coordinates of a blackbody radiator with temperatures from1,000 to 20,000 Kelvin is called the Planckian locus. Colours on this locus in the rangefrom 2,500 to 20,000 K are considered to be white, with 2,500 K being reddish white and20,000 K being bluish white (warm to cool white). See also: Black Body Radiation;Correlated Colour Temperature.Cone (Receptor)Firespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 15. 14 | P a g eThe visual receptor in the retina of the human eye responsible for daylight adapted, colourvision. There are three types of cones, each sensitive to red, green or blue wavelengths. Seealso: Retina; Rod.CorneaThe transparent front part of the human eye. To use an engineering analogy, the corneafunctions as a "dust cap" and also performs primary focussing of the light rays into the eye.Correlated Colour Temperature (CCT)Correlated Colour Temperature (CCT) describes the colour temperature of those white lightsources whose colours don‟t fall exactly on the Planckian locus (i.e. for non blackbodyemitters). The CCT of a non-Planckian source is the blackbody colour temperature that thesource resembles most closely. Correlated colour temperature is reported in units of Kelvin(K). CCT can be considered to be a simplified metric for describing the colour of a white lightsource. For coloured light sources, dominant wavelength can be used to express colour in asingle number. See also: Colour Temperature; Dominant Wavelength.Cosine DiffuserAn object which exhibits Lambertian like reflectance or transmittance. Transmissiondiffusers are used in photometry to impart a cosine response at the input to a detector tocorrect for the effective illuminance of off-axis rays, or to more uniformly illuminate a multi-element detector. Thin sheets of ground glass (quartz), PTFE as well as the input port of anintegrating sphere all function as effective transmission diffusers. See also: CosineResponse.Cosine ResponseThe Lambertian spatial response of a perfect reflecting or transmitting diffuser whereby theintensity from or through the surface varies with the cosine of the angle subtended betweenthe direction of view and the normal to the surface. Applies to light meters (radiometers andphotometers) designed for measuring irradiance or illuminance which should apply a cosineangular response to light rays received at angles other than normal incidence, typicallyachieved using a transmission diffuser or integrating sphere. See also: Cosine Diffuser;Lambertian.CRTAcronym. Stands for Cathode Ray Tube. The type of television display that was popularbefore the introduction of flat panel displays (LCD, OLED, RPTV & plasma).Diode ArrayA detector that comprises a linear array of segmented photodiode detectors. See also:Photodetector; Photodiode; Spectroradiometer.Dominant WavelengthFirespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 16. 15 | P a g eDominant wavelength is a useful measure of the effective wavelength (in nm) of non-monochromatic light sources, in particular LEDs. It is defined in relation to a specifiedstandard illuminant (usually Illuminant E, but this is arbitrary). It is a measure of the hue(or colour sensation) produced by the light source. Not to be confused with peakwavelength. Dominant wavelength is normally applied to coloured LEDs whereas correlatedcolour temperature is applied to white LEDs.DuraflectLabspheres proprietary, waterproof, diffuse white coating for the UV-VIS-NIR spectralregion (350-1200nm).ElectroluminescenceThe emission of light as a result of the passage of an electrical current. Distinct fromincandescence which is the emission of light as a result of heat. See also: LED.Electromagentic RadiationElectromagnetic radiation is generated by the motion of electrically charged particles.Optical radiation, light, X-rays, radio waves and microwaves are all examples ofelectromagnetic radiation. See: Light; Optical Radiation.EULUMDAT (File)A standardised data file which expresses the light output of a luminaire as luminousintensity versus angle. EULUMDAT files are assigned the file extension ".ldt". Used bylighting designers to model the illumination performance of a lighting scheme usingcommercial lighting design programmes. An EULUMDAT file is commonly referred to as"photometric data" for a luminaire. See also: Goniophotometer; IES (file).Far FieldIn photometry, that distance from a lamp (called the photometric distance) where theemitter is considered to be a point source, usually at a distance of between 5-10 times thesource diameter (although this is not the case for LEDs). Intensity measurements areperformed in the far field, in which the inverse squared law applies. See also: Near Field;Intensity; Average Intensity; Inverse Squared Law; Point Source; Photometric Distance.FluorescenceThe emission of light at a longer wavelength as a result of absorption of light at a shorterwavelength in a fluorescent material. Applies for that case whereby the emission occurs atthe same time as the absorption. See also: Luminescence; Phosphorescence.Fluorescent LampA lamp comprising a glass tube filled with mercury gas and coated on its inner surface witha phosphor. When the gas is charged with an electrical current, ultraviolet radiation isproduced. This in turn is absorbed in the phosphor, causing it to emit visible light by theprocess of fluorescence. See also: CFL; Fluorescence.Firespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 17. 16 | P a g eFoot-candle (fc)The English unit of illuminance. One foot-candle (fc) equals one lumen per square foot,which equals 10.76 lux. See also: Illuminance; Lux.Foot-Lambert (fL)The English unit of luminance. One foot-Lambert (fL) equals 1/π candelas per square foot,which equals 3.426 candelas per sq. meter. See also: Luminance.FoviaThat part of the eye‟s retina that has the greatest density of cones. See also: Retina, Cone.GoniometerA goniometer is an (electro) mechanical positioning device which allows one to change therelative angle (φ, θ) at which a photometer (also a spectroradiometer or colorimeter) views alight source. This can be accomplished by either moving the detector around a stationarysource or by tipping and tilting the source whilst the detector remains in a fixed position.See also: Goniophotometer.GoniophotometerAn instrument which performs measurements of the (far-field) luminous intensity orilluminance or (near-field) luminance of a light source as a function of viewing angle. Canalso be used to measure the total luminous flux of a light source by measuring thedirectional luminous intensity and integrating over 4π steradians. A goniophotometer iscommonly used to measure so-called "photometric data" for luminaires. Photometric data inthis context is the light output (luminous intensity) as a function of angle presented inindustry-standard file formats. See also: EULUMDAT; Goniometer; IES.HueThe perceived colour of a light source.IES (File)A standardised data file which expresses the light output of a luminaire as luminousintensity versus angle. Derives from the acronym for the Illuminating Engineering Society ofNorth America (IESNA). IES files are assigned the file extension ".ies". Used by lightingdesigners to model the illumination performance of a lighting scheme using commerciallighting design programmes. An IES file is commonly referred to as "photometric data" for aluminaire. See also: EULUMDAT (file); Goniophotometer.IlluminanceIlluminance (Ev) is the luminous flux received per unit area. Illuminance is measured in lux(lx) where 1 lux equals 1 lumen per square meter. See also: Foot-candle.Illuminant AFirespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 18. 17 | P a g eIlluminant A (CIE) represents the colour temperature of an incandescent lamp (2856K). Seealso: Standard Illuminant; Colour Temperature.Illuminant BIlluminant B (CIE) represents the colour temperature of direct sunlight (4874K). See also:Standard Illuminant; Colour Temperature.Illuminant CIlluminant C (CIE) represents the colour temperature of indirect sunlight (6774K). See also:Standard Illuminant; Colour Temperature.Illuminant DIlluminant D (CIE) represents the colour temperature of daylight. There are severalstandard illuminants in the D series including D50 which represents bright incandescentlight (5000K) and D65 which represents natural daylight (6504K). See also: StandardIlluminant; Colour Temperature.Illuminant EIlluminant E (CIE) is the colour temperature of an artificial, normalising source (5500K).Has chromaticity coordinates of x=0.3333 & y=0.3333. See also: Standard Illuminant;Colour Temperature.Illuminant FIlluminant F (CIE) represents the correlated colour temperature of light from a fluorescentlamp. There are several standard illuminants in the F series including F2 which representscool white light (4200K), F7 which represents broadband daylight (6500K) and F11 whichrepresents a narrow band white lamp (4000K). See also: Standard Illuminant; ColourTemperature.Imaging Photometer (Colorimeter)A photometric instrument capable of spatially-resolved luminance, illuminance and colourmeasurements. Sometimes referred to as a video photometer. Employs a CCD detector.IncandescenceLight that is emitted by thermal radiation at a temperature high enough to be visible.Incandescent LampA lamp which emits light as a result of resistive heating when an electrical current passesthrough a metal wire in a vacuum.InfragoldFirespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 19. 18 | P a g eLabspheres proprietary electro-plated gold coating for the infrared spectral region(>800nm).InfraredDescribing that part of the electromagnetic spectrum comprising optical radiation havingwavelengths longer than 780nm but shorter than 1mm. Infrared radiation is not visible tothe naked eye.Integrating SphereA hollow, spherical chamber with a diffuse, high reflectance interior coating. Used inphotometry to measure the total luminous flux (power) of a light source.IntensitySee: Luminous IntensityInverse Squared LawDescribes the relationship between the illuminance from a light source which varies ininverse proportion to the square of the distance from the source. Applies to the case of apoint source of light in the photometric far-field. See also: Far-Field; Illuminance; PointSource.IrisThe variable, limiting aperture found in the human eye.IrradianceIrradiance (Ee) is the radiometric analogue of illuminance, the radiant flux received per unitarea. Irradiance is measured in Watts per square meter.IsotropicA light source is isotropic when it radiates with equal intensity (flux per unit solid angle) inall directions. Not to be confused with Lambertian.Kelvin (K)The unit of measurement of colour temperature and correlated colour temperature. TheKelvin scale starts at absolute zero (-273°C). See also: Colour Temperature; CorrelatedColour Temperature.Lamberts Cosine LawSee Lambertian.LambertianFirespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 20. 19 | P a g eA Lambertian surface is one that reflects (or transmits) with equal radiance or luminance inall directions. In other words, the reflected (transmitted) intensity (flux pew unit solid angle)from a Lambertian surface varies in proportion to the cosine of the angle subtendedbetween the direction of view and the surface normal. See also: Cosine Response.LaserFrom the acronym for Light Amplification by the Stimulated Emission of Radiation. A lightsource typically characterised by a combination of coherence, narrow spectral linewidth anda collimated beam. The term "laser light" refers to electromagnetic radiation withwavelengths between 150nm up to 11µm. A laser was first demonstrated in 1960 byTheodore H Maiman working at the Hughes Corporation, although the term „laser‟ was firstcoined by Gordon Gould of Columbia University.LCDAcronym. Stands for Liquid Crystal Display.LEDAcronym. Stands for Light Emitting Diode. LEDs are solid state light sources whichgenerate light by electroluminescence when an electrical current is passed through asemiconductor p-n junction. See also: Electroluminescence; OLED.LightLight is a term that we use to define that part of the electromagnetic radiation that humanscan see (“visible light”). Visible light has a wavelength bteween 380 and 780nm. Moreaccurately described as optical radiation, it forms part of the electromagnetic spectrum thatencompasses radio waves, microwaves, x-rays and gamma rays. Optical radiation is thatwhich obeys wave-like behaviour, as opposed to particle-like.LightnessSee Chroma.LinewidthDenotes the spectral purity or width in wavelength of a light source. The spectral width of alight source is normally defined as the full width half max (FWHM) linewidth. The termbandwidth is often used interchangeably with linewidth.LORAcronym. Stands for Light Output Ratio. Being the ratio of the luminous flux produced by aluminaire to that produced by the lamp (or lamps) fitted to the luminaire. A measure of theefficiency of a luminaire. See also: Luminaire; Luminous Flux.Lumen (lm)The SI unit of luminous flux (lm).Firespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 21. 20 | P a g eLuminaireA light fitting which generally comprises a lamp in a housing together with a reflectorand/or lens. May include control gear (drive electronics).LuminanceLuminance (Lv) is the luminous flux emitted per unit solid angle and per unit area. In the SIsystem, luminance is measured in candelas per square meter where 1 cd/m2 equals 1lumen per steradian per square meter. The photometric analogue of radiance. Luminance isa near-field measurement of a light source; luminous intensity is the measurement made inthe photometric far-field. See also: Far-Field; Foot-Lambert; Luminous Intensity; Near-Field;Nit; Steradian.LuminescenceLuminescence can be taken to describe the process of fluorescence or phosphorescence.See: Fluorescence, Phosphorescence.Luminous EfficacyThe efficiency of a light source, the quotient of the luminous flux emitted divided by theelectrical power consumed. Reported in units of lumens per Watt (lm/W).Luminous ExitanceLuminous exitance (Mv) is the luminous flux emitted from a surface per unit area, measuredin units of lumens per square meter. Geometrically equivalent to illuminance, luminousexitance is not however reported in lux.Luminous FluxThe luminous flux (Fv) or more correctly the total luminous flux of a light source is the totalphotometric power emitted in all directions. Luminous flux is measured in lumens (lm),which is the photometric analogue of the Watt.Luminous IntensityThe luminous intensity (Iv) in a given direction (often abbreviated to intensity, sometimesreferred to as beam candela) is the photometric power from a point source emitted per unitsolid angle. Intensity is measured in the SI base unit of the candela (cd) where 1 candelaequals 1 lumen per steradian. Luminous intensity is a far-field measurement of a lightsource; luminance is the measurement made in the photometric near-field. See also: Far-Field; Luminance; Near-Field; Steradian.Lux (lx)The SI unit of illuminance (lx).Mean Spherical Candle Power (MSCP)Firespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 22. 21 | P a g eMean Spherical Candle Power (M.S.C.P.) is the luminous flux of a light source divided by 4πsteradians.MesopicPhotopic (cone) vision operates when the eye sees luminance levels of ≥ 3 candelas persquare meter, whereas scotopic (night time) vision operates when the luminance falls below0.01 candelas per square meter. For luminance levels between 0.01 and 3 cd/m 2, both rodsand cones contribute to the vision process to varying degrees. This "in-between" region iscalled mesopic, and research is ongoing into the development of a standard observerfunction for mesopic vision. See also: Photopic; Scotopic.Micrometer (µm)A unit of wavelength, normally used to describe infrared radiation. Often abbreviatedto micron. One micrometer or micron (µm) equals 1 x 10-6 meters. One micrometer alsoequals 1000 nanometers (nm).MonochromaticLight that is composed of a single wavelength or colour (hue), having 100% purity and anarrow linewidth.MonochromatorSee Spectrometer.Nanometer (nm)A unit of wavelength of light, normally used to describe visible light. One nanometer (nm)equals 10-9 meters.Near-FieldIn photometry, that region close to a lamp where the emitter is not considered to be a pointsource, usually at a distance of less than 5-10 times the source diameter (although this isnot the case for LEDs). Intensity measurements are performed in the far field, in which theinverse squared law applies. See also: Far Field, Intensity, Average Intensity, InverseSquared Law, Point Source.NitA historically significant unit of luminance. Derives from the Latin "to illuminate". One nitequals 1 candela per square meter. See also: Luminance.OLEDAcronym. Stands for Organic Light Emitting Diode. A type of light emiting diode (LED) withan emissive electroluminescent layer made of organic compunds. Related devices are LightEmitting Polymers (LEPs). See also: Electroluminescence; LED.Firespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 23. 22 | P a g eOptical Density (OD)Describes the level of attenuation of light as it passes through an optical filter. The higherthe OD value, the higher the attenuation (and the higher the protection). OD increases withincreasing thickness of absorptive filters. Optical density is the logarithm (to the base ten)of the reciprocal of the transmittance. For example, an OD of 1 means 10%, an OD of 2means 1% and an OD of 3 means 0.1% transmittance (and so on)Optical RadiationDescribing that part of the electromagnetic spectrum comprising rays that exhibit a wave-like property (as opposed to particle-like). Includes ultraviolet, visible (light) and infraredradiation.PhosphorescenceThe emission of light at a longer wavelength as a result of absorption of light at a shorterwavelength in a phosphorescent material. Applies for that case whereby the emissionoccurs after the absorption. See also: Fluorescence, Luminescence.PhotodetectorA generic name given to a device that detects optical radiation. See also: Photodiode;PMT; Diode Array; CCD.PhotodiodeA discrete semiconductor photodetector that produces a photocurrent the magnitude ofwhich is proportional to the level of light received when illuminated by optical radiation. Inphotometers, the detector is based on silicon with a photopic filter; the combined detectorplus filter is designed to provide a spectral responsivity scaled to match that of the photopicresponse, the CIE standard observer for photopic vision.Photometric DistanceThat distance from a light source that defines the far field. In the photometric far-field,illuminance (irradiance) varies in inverse proportion to the square of the distance form thelight source. See also: Inverse Squared Law; Far-Field; Near-Field.PhotometerAn optical instrument that measures a defined geometric property of visible light with aphotopic spectral response matching that of the human eye. See also: Photopic;Radiometer; Spectroradiometer.PhotometryThe science of measuring optical radiation with a photopic spectral response matching thatof the human eye. See also: Photopic; Radiometry; Spectroradiometry.Photomultiplier Tube (PMT)Firespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 24. 23 | P a g eA photomultiplier tube (PMT) is a photodetector that comprises a photocathode which isheld in vacuum and emits electrons when exposed to light. This charge is accelerated by ahigh voltage field causing the electrons to hit a metal plate, whereupon more electrons areemitted (the multiplier effect). Not normally used in photometers, PMTs are commonly usedin traditional scanning spectroradiometer (monochromator) systems.Photopic (Response)The daylight-adapted relative spectral response of the eye is called the spectral luminousefficiency function for photopic vision, V(l). This is an empirical distribution that was firstadopted in 1924. Applies for luminance values above 3cd/m 2 to the spectral range between380 and 780nm having a peak response at 555nm. The photopic response explains why thehuman eye is more sensitive to green light than blue or red light. At luminance levels below3cd/m2, the eye transitions through a mesopic response. At luminance levels at or below0.01 cd/m2, the eye becomes dark adapted and possesses a scoptic response. See also:Mesopic; Scotopic.PixelThe individual detector element in a two-dimensional CCD detector array. See also: CCD.Plankian LocusThe locus of points on the CIE chromaticity diagram that plots the chromaticity ofblackbody radiators of differing colour temperatures.Plankian RadiatorA synonym for blackbody radiator.Point SourceA light source is considered to be a point source if it is observed at a position at or beyondthe photometric distance, that is, the far-field. See also: Intensity; Average Intensity; Far-Field; Photometric Distance.PolychromaticUsed to describe optical radiation that is comprised of multiple discrete wavelength orhaving a continuous spectrum.Primary ColourIn colorimetry, primary (additive) colours are red, green and blue, and their subtractiveopposites cyan, magenta and yellow. See also: Additive Primary Colours; SubtractivePrimary Colours.PurityPurity is a measure of the degree of saturation of a light source, reported as a percentage. Itis defined with respect to a specified standard illuminant (usually illuminant E, but thisFirespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 25. 24 | P a g earbitrary). As most (coloured) LEDs have a narrow spectral emission (that is, near-monochromatic), they have a purity of close to 100% (in other words, the colour cannot bedistinguished from a true monochromatic light source). See also: Saturation.RadianceRadiance (Le) is the radiant flux emitted per unit solid angle and per unit area. Radiance ismeasured in Watts per steradian per square meter. The radiometric analogue of luminance.Radiant ExitanceRadiant exitance (Me) is the radiant flux emitted from a surface per unit area, measured inunits of Watts per square meter. Geometrically equivalent to irradiance and the radiometricanalogue of luminous exitance.Radiant FluxThe radiant flux (Φe) - more correctly the total radiant flux - of a light source is the totalpower emitted in all directions. Radiant flux is measured in Watts (W), which is theradiometric analogue of the lumen.Radiant IntensityThe radiant intensity (Ie) in a given direction (often abbreviated to intensity) is the radiantflux from a point source emitted per unit solid angle. Intensity is measured in units ofWatts per steradian. The radiometric analogue of luminous intensity.RadiometerAn optical instrument that measures the absolute amount of a defined geometric propertyof light. A laser power meter is a type of radiometer. See also: Photometer;Spectroradiometer.RadiometryThe science of measuring the absolute amount of optical radiation.RetinaThe light-sensitive area on the rear of the human eye containing photo-receptors. The areacontaining the highest concentration of photo-receptors is called the fovea. See also: Rod;Cone; Fovea.RGBMeaning Red, Green & Blue which are the additive primary colours. Used in relation to thehuman eye‟s tristimulus colour response. See also: Additive Primary Colour.RodFirespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 26. 25 | P a g eThe visual receptor in the retina of the human eye responsible for scotopic (night-time,monochromatic) vision. See also: Retina; Cone.SaturationThe attribute of colour perception that describes the degree of departure of the colour fromthe neutral grey of the same lightness. See also: Purity.ScotopicThe dark-adapted relative spectral response of the eye is called the spectral luminousefficiency function for scotopic vision, V‟(l). The scotopic response was first adopted by CIEin 1951 and applies to the spectral region between 380 and 780nm, with a peak at 507nm.The Scotopic response applied to luminance levels of 0.01 cd/m2 of less. See also: Mesopic;Photopic.SISysteme Internationale d‟Unites, the international metric system of measurement units.Silicon PhotodiodeSee Photodiode.Solid AngleSee Steradian.Spectral Power Distribution (SPD)The power distribution of a light source as a function of wavelength. Determines the colour,colour temperature and colour rendering properties of a light source.SpectraflectLabspheres proprietary white reflectance coating. The coating is barium sulphate basedand hydroscopic. Available as a coating service and as a liquid paint (6080) for userapplication. Best applied by spray painting.SpectralonLabspheres patented diffuse reflectance material. A solid thermoplastic which exhibits thehighest diffuser reflectance of any material in the 250-2500nm range. Integrating spheresand reflectors are machined from a block of Spectralon. Spectralon is widely used as awhite reflectance standard (99%). Can be doped with inorganic materials to create greyscale standards (2-80%), colour standards, wavelength standards and fluorescencestandards.SpectrometerFirespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 27. 26 | P a g eAn instrument that separates polychromatic light into its constituent wavelengths. Employsa dispersive optical element, usually a diffraction grating. A spectroradiometer and aspectrophotometer comprise a spectrometer combined with a detector, normally a CCDarray. A (scanning) monochromator is a form of spectrometer in which the diffractiongrating rotates to transmit one wavelength at a time, whereas a CCD spectrometer analysesa wide range of wavelengths simultaneously.SpectroradiometerAn instrument for measuring the radiant power from a light source as a function ofwavelength. Normally combines a spectrometer with a photodetector or CCD. Can be usedto more accurately calculate the photometric and colorimetric properties of a light sourcethan a photometer or colorimeter by multiplying the spectral radiant power by standardphotopic and tristimulus observer functions.SpectrumThe spectral arrangement of electromagnetic energy in order of wavelength. See also:Spectral Power Distribution (SPD).Spectrum LocusThe plot of the chromaticity coordinates of monochromatic light in the CIE colour spacediagram. See also: Chromaticity Diagram (CIE).Standard IlluminantSee CIE Standard Illuminant.Standard ObserverSee: CIE Standard Observer Function.SteradianThe steradian is the (dimensionless) unit of solid angle. A sphere contains 4π steradians(and by definition, a hemisphere comprises 2π steradians). A steradian is that solid anglesubtended from the centre of a sphere by a spherical surface area having an area equal tothe square of the radius. In other words, the steradian solid angle of a beam of light is equalto the projected area divided by the square of the distance.Subtractive Primary ColourThe subtractive primary colours are Cyan, Magenta & Yellow. When inks of these coloursare applied to white paper in equal amounts, these combine to produce black. Combiningtwo subtractive primaries in equal amounts creates an additive primary colour. See also:CMYK; Additive Primary Colour.ThermopileFirespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 28. 27 | P a g eA broadband detector (thermal rather than optical) that is commonly used in the radiometryof lasers. Comprises an array of thermocouple junctions.TristimulusDescribing the RGB 2° colour matching functions, which CIE transformed into the XYZcolour matching functions. The XYZ functions define the CIE 1931 standard colorimetricobserver. The Y channel (green) was chosen to match that of the photopic response, so thatcolour measurement instruments could double as photometers. For observer fields of viewof greater than 2°, CIE published its 1964 supplementary standard colorimetric observer.(CIE) u Chromaticity CoordinateTogether with the CIE v chromaticity coordinate provides a numeric description of colour.The CIE u chromaticity coordinate is plotted as the abscissa (horizontal axis) on the two-dimensional colour space graph defined by CIE to communicate the colour of a light source.The CIE v chromaticity coordinate is plotted as the ordinate (vertical axis). Refers to the CIE10° tristimulus observer function (1964) as plotted in the 1976 uniform colour spacechromaticity diagram. The intersection of u and v within the CIE colour space diagramuniquely defines the colour of a light source. See also: Chromaticity Coordinates;Chromaticity Diagram; Tristimulus; (CIE) x; (CIE) y.Ultraviolet (UV)Describing that part of the electromagnetic spectrum comprising optical radiation havingwavelengths between 100 and 400nm. Ultraviolet (UV) radiation is absorbed in the lens orcornea and is not visible to the naked human eye.UVAThat part of the Ultraviolet spectral range with wavelengths between 315 and 400nm.UVBThat part of the Ultraviolet spectral range with wavelengths between 280 and 315nm.UVCThat part of the Ultraviolet spectral range with wavelengths between 100 and 280nm.(CIE) v Chromaticity CoordinateTogether with the CIE u chromaticity coordinate provides a numeric description of colour.The CIE v chromaticity coordinate is plotted as the (vertical axis) on the two-dimensionalcolour space graph defined by CIE to communicate the colour of a light source. The CIE uchromaticity coordinate is plotted as the abscissa (horizontal axis). Refers to the CIE 10°tristimulus observer function (1964) as plotted in the 1976 uniform colour spacechromaticity diagram. The intersection of u and v within the CIE colour space diagramuniquely defines the colour of a light source. See also: Chromaticity Coordinates;Chromaticity Diagram; Tristimulus; (CIE) x; (CIE) y.Firespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 29. 28 | P a g eVisible (Light)Describing that part of the electromagnetic spectrum comprising optical radiation havingwavelengths between 380 and 780nm that can be detected by the retina in the human eye.Wavelengths in this range combine to create the sensation of colour.V(λ) FunctionSee Photopic.Watt (W)The SI unit of power and radiant flux.WavelengthThe periodic peak-to-peak distance in an electromagnetic wave. For ultraviolet and visiblelight, defined in nanometers (nm); for infrared light, defined in micrometers (µm).White LightLight that appears to be white. Can contain a continuous spectrum of light (as from thesun) or comprise as few as two colours. White light comprising two colours exhibits poorcolour rendering. Light on the Planckian locus (blackbody curve) on the CIE chromaticitydiagram with colour temperatures between 2500 and 20000K is considered to be “white”.See also: CIE Standard Illuminant.(CIE) x Chromaticity CoordinateTogether with the CIE y chromaticity coordinate provides a numeric description of colour.The CIE x chromaticity coordinate is plotted as the abscissa (horizontal axis) on the two-dimensional colour space graph defined by CIE to communicate the colour of a light source.The CIE y chromaticity coordinate is plotted as the ordinate (vertical axis). Refers to the CIE2° tristimulus observer function (1931). The intersection of x and y within the CIE colourspace diagram uniquely defines the colour of a light source. See also: ChromaticityCoordinates; Chromaticity Diagram; Tristimulus; (CIE) u; (CIE) v.(CIE) y Chromaticity CoordinateTogether with the CIE x chromaticity coordinate provides a numeric description of colour.The CIE y chromaticity coordinate is plotted as the (vertical axis) on the two-dimensionalcolour space graph defined by CIE to communicate the colour of a light source. The CIE xchromaticity coordinate is plotted as the abscissa (horizontal axis). Refers to the CIE 2°tristimulus observer function (1931). The intersection of x and y within the CIE colourspace diagram uniquely defines the colour of a light source. See also: ChromaticityCoordinates; Chromaticity Diagram; Tristimulus; (CIE) u; (CIE) v.Firespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 30. 29 | P a g e Lumen Method Calculations The lumen method is based on fundamental lighting calculations. The lumen method formula is easiest to appreciate in the following form. (1) where E = average illuminance over the horizontal working plane n = number of lamps in each luminaire N = number of luminaire F = lighting design lumens per lamp, i.e. initial bare lamp luminous flux UF = utilisation factor for the horizontal working plane LLF = light loss factor A = area of the horizontal working plane 2.1 Light Loss Factor Light loss factor (LLF) is the ratio of the illuminance produced by the lighting installation at the some specified time to the illuminance produced by the same installation when new. It allows for effects such as decrease in light output caused by (a) the fall in lamp luminous flux with hours of use, (b) the deposition of dirt on luminaire, and (c) reflectances of room surfaces over time. In fact, light loss factor is the product of three other factors:Firespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 31. 30 | P a g e (2) where LLMF = lamp lumen maintenance factor LMF = luminaire maintenance factor RSMF = room surface maintenance factor 2.1.1 Lamp Lumen Maintenance Factor Lamp lumen maintenance factor (LLMF) is the proportion of the initial light output of a lamp produced after a set time to those produced when new. It allows for the decline in lumen output from a lamp with age. Its value can be determined in two ways: (a) by consulting a lamp manufacturers catalog for a lumen depreciation chart, and (b) by dividing the maintained lumens by the initial lamps. 2.1.2 Luminaire Maintenance Factor Luminaire maintenance factor (LMF) is the proportion of the initial light output from a luminaire after a set time to the initial light output from a lamp after a set time. It constitutes the greatest loss in light output and is mainly due to the accumulation of atmospheric dirt on luminaire. Three factors must be considered in its determination: (a) the type of luminaire, (b) atmospheric conditions, and (c) maintenance interval. 2.1.3 Room Surface Maintenance Factor Room surface maintenance factor (RSMF) is the proportion of the illuminance provided by a lighting installation in a room after a set time compared with that occurred when the room was clean. It takes into account that dirt accumulates on room surfaces and reduces surface reflectance. Figure 4 shows the typical changes in the illuminance from an installation that occur with time due to dirt deposition on the room surfaces.Firespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 32. 31 | P a g e 2.2 Utilisation Factor Utilisation factor (UF) is the proportion of the luminous flux emitted by the lamps which reaches the working plane. It is a measure of the effectiveness of the lighting scheme. Factors that affect the value of UF are as follows: (a) light output ratio of luminaire (b) flux distribution of luminaire (c) room proportions (d) room reflectances (e) spacing/mounting height ratio 2.2.1 Light Output Ratio of Luminaire Light output ratio of luminaire (LOR) takes into account for the loss of light energy both inside and by transmission through light fittings. It is given by the following expression. (3) Example 1 The total, upward and downward lamp output from a lamp are 1000 lm, 300 lm and 500 lm respectively. Calculate upward light output ratio (ULOR), downward light output ratio (DLOR), light output ratio (LOR) of luminaire and percentage of light energy absorbed in luminaire.Firespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 33. 32 | P a g e Amount of light energy absorbed in luminaire = 100 - 80 = 20 % A greater DLOR usually means a higher UF. A simple classification of luminaires according to their distribution is based on flux fractions, as shown in Figure 5. Upward flux fraction (UFF) and downward flux fraction (DFF) are used as a basis of comparison. Example 2 For data given in Example 1 determine upward flux fraction (UFF), downward flux fraction (DFF) and flux fraction ratio (FRR).Firespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 34. 33 | P a g e Figure 5 Flux Fraction of Various Luminaires 2.2.2 Flux Distribution of Luminaire Direct ratio is the proportion of the total downward luminous flux from a conventional installation of luminaires which his directly incident on the working plane. It is used to assess the flux distribution of luminaire. Since the intensity distribution pattern of the light radiated from a luminaire in the lower hemisphere will affect: (a) the quantity of the downward flux falls directly on the working plane and (b) the quantity of flux available for reflection from the walls in a given room, Direct ratio depends on both the room proportions and the luminaires. Direct ratio has a low value with a narrow room (small room index) and a luminaire which emits most of its light sideways (BZ 10), and on the contrary, a high value with a wide room (large room index) and a luminaire which emits most of its light downwards (BZ 1). 2.2.3 Room Proportion Room index (RI) is the ratio of room plan area to half the wall area between the working and luminaire planes. (4) where L = length of room W = width of room Hm = mounting height, i.e. the vertical distance between the working plane and the luminaire. 2.2.4 Room Reflectances The room is considered to consist of three main surfaces: (a) the ceiling cavity, (b) the walls, andFirespec Engineering (M) Sdn Bhd By: Hj Azlan Abass
  • 35. 34 | P a g e (c) the floor cavity (or the horizontal working plane). The effective reflectances of the above three surfaces affect the quantity of reflected light received by the working plane. 2.2.5 Spacing to Height Ratio Spacing to Height ratio (SHR or S/Hm) is defined as the ratio of the distance between adjacent luminaires (centre to centre), to their height above the working plane. For a rectangular arrangement of luminaires and by approximation, (5) where A = total floor area N = number of luminaires Hm = mounting height Under a regular array of luminaires the illuminance on the working plane is not uniform. The closer spaced the luminaires for a given mounting height, the higher the uniformity; or the greater the mounting height for a given spacing, the greater the uniformity. If uniformity of illuminance is to be acceptable for general lighting, (a) SHR should not exceed maximum spacing to height ratio (SHR MAX) of the given luminaire as quoted by the manufacturer, and (b) geometric mean spacing to height ratio of the luminaire layout should be within the range of nominal spacing to height ratio (SHR NOM) of the given luminaire as quoted by the manufacturer, i.e. (6)Firespec Engineering (M) Sdn Bhd By: Hj Azlan Abass