| Close Glossary |
|
Item |
Definition |
| Absolute Photometry |
Photometry is the measurement of the properties of light, particularly intensity. Absolute photometry, used for conventional lamps and luminaires with… More » |
| Action Spectrum |
The magnitude of a given stimulus required to produce a fixed physiological response, plotted against wavelength. The action spectrum reveals… More » |
| Adaptation |
The process by which the retina becomes accustomed to more or less light than it was exposed to during an… More » |
| Adaptation luminance |
The luminance to which the visual system is assumed to be adapted. In practice, this is usually taken to be… More » |
| Adaptive compensation |
Control strategy in which light levels are reduced during evening hours to accommodate human lighting preferences at night and save… More » |
| Altitude |
The vertical angular distance of a point in the sky above the horizon. Altitude is measured positively from the horizon… More » |
| Amalgam |
An alloy of mercury with other metals. Some CFLs use a mercury amalgam rather than standard mercury. An amalgam keeps… More » |
| Ambient lighting |
Lighting throughout an area that produces general illumination that may or may not be uniform. Original Chapter Source: Luminaires Provided… More » |
| ANSI |
American National Standards Institute Original Chapter Source: Policies & Programs More » |
| Aperture |
In buildings, an aperture is an opening, such as a window or a skylight, that allows daylight to enter the… More » |
| Application efficiency |
A lighting design metric that looks at the fraction of of light (lumens) at the point of use (visual task)… More » |
| Aqueous humor |
The transparent, watery fluid between the cornea and the lens of the eye. Original Chapter Source: Health & Performance Provided… More » |
| ASHRAE |
American Society of Heating, Refrigerating, & Air-Conditioning Engineers Original Chapter Source: Policies & Programs More » |
| Atrium |
A multistoried space within a building that allows daylight to illuminate the adjacent interior spaces typically through a large overhead… More » |
| Auxiliaries |
Electrical devices that provide proper voltage to ignite light sources and regulate current during normal operation. Examples include ballasts, transformers… More » |
| Azimuth |
The horizontal angular distance between the vertical planes containing two points in the sky. The azimuth of a single point… More » |
| Ballast |
The ballast is an electrical device that performs two basic functions: 1) provides the starting voltage and 2) limits the… More » |
| Ballast Efficacy Factor (BEF) |
Sometimes called ballast efficiency factor, ballast efficacy factor is the ratio of the ballast factor to the active power (in… More » |
| Ballast efficiency |
Metric used to express the electrical efficiency of a ballast, measured as the lamp wattage divided by the input watts… More » |
| Ballast factor |
Ballast factor (BF) The ratio of the light output of a fluorescent lamp or lamps operated on a ballast to… More » |
| Basis of Design |
Document produced during the design phase, and refined over the remainder of the project, that clearly articulates the design intent… More » |
| Bi-level switching |
Control of lighting system involving dual-circuiting a lighting system, which enables two different light and power levels in addition to… More » |
| Binning (LED) |
The system used by an LED package manufacturer to separate their LEDs into groups with similar performance attributes. LEDs are… More » |
| Biosphere |
The global sum of all ecosystems, all living things. Original Chapter Source: Policies & Programs More » |
| Black body locus |
The collection of points (locus) on a chromaticity diagram that describes the color of blackbody as a function of temperature. … More » |
| Brightness |
The attribute by which an area of finite size is perceived to emit, transmit, or reflect a greater or lesser… More » |
| British Thermal Unit (BTU) |
Unit of measurement for heat energy equal to about 1,055.06 joules, or the amount of thermal energy required to raise… More » |
| BTU |
See British Thermal Unit. More » |
| California?s Title 24 Building Energy Code |
The Energy Efficiency Standards for Residential and Nonresidential Buildings were established in 1978 in response to a legislative mandate to… More » |
| Candela |
Unit of luminous intensity. The measurement of light intensity emitted in a specific direction from a luminaire. Original Chapter Source:… More » |
| Candela distribution chart |
See candela distribution table Original Chapter Source: Luminaires Provided By: Craig DiLouie More » |
| Candela distribution curve |
Graphical representation of select data in the candela distribution table, visually depicting the relative light intensity for a single vertical… More » |
| Candela distribution table |
Element of luminaire photometric report typically presented in the manufacturer catalog sheet for the product. The table, also called the… More » |
| Candela per square meter (Cd/m2) |
Unit of luminance in the metric system. The English unit equivalent is candelas per square foot (Cd/ft2). Original Chapter Source:… More » |
| Candlepower |
The measure of the intensity of a light source in a given direction, measured in candelas (Cd). Candlepower distribution curves… More » |
| Carbon neutral |
Total operations that release zero carbon dioxide into the atmosphere. Original Chapter Source: Luminaires Provided By: Leslie North More » |
| Cataract |
A common cause of partial sight. Cataract is the formation of an opacity in the eye, usually in the lens,… More » |
| Cathode sputtering |
The process by which cathode material is slowly eroded away by electron mercury ion bombardment. Original Chapter Source: Sources Provided… More » |
| Chorio-retinal injury |
Thermal damage to the retina produced by focusing visible and infrared radiation up to 1400 nm onto the retina. Original… More » |
| CIE |
Commission Internationale de l'Eclairage (International Lighting Commission) Original Chapter Source: Luminaires Provided By: Naomi Miller More » |
| Circadian rhythms |
Circadian rhythms are physical, mental and behavioral changes that follow a roughly 24-hour cycle, responding primarily to light and darkness… More » |
| Circadian system |
The physiology of the body that controls the 24 hour variation in hormonal balance and, consequently, activity and behavior. Original… More » |
| Circumsolar area |
The region of very high brightness around the solar disk. Original Chapter Source: Daylighting Provided By: Kosta Papamichael / CLTC More » |
| Clerestory |
The part of a building rising clear of the roofs or other parts, whose walls contain windows for lighting the… More » |
| Closed loop |
Photocontrol system that measures combined daylight/electric light level on a representative task surface in the controlled space and adjusts light… More » |
| CMH lamp |
The designation for ceramic metal halide lamps in which the arc tube material is a ceramic rather than quartz. Original… More » |
| Coefficient of utilizaton (CU) |
Coefficient of Utilization (CU) is the percentage of light generated by the lamps in a luminaire that reaches the work… More » |
| Color Rendering Index (CRI) |
A scale of values from to 100, indicating how a light source makes a material color look compared to… More » |
| Color Temperature or Correlated Color Temperature (CCT) |
A specification of the apparent color of a light source relative to the color appearance of an ideal incandescent source… More » |
| Commissioning |
A systematic process that ensures that all elements of the lighting control system perform interactively and continuously according to documented… More » |
| Compact Fluorescent Lamp (CFL) |
A fluorescent lamp using compact folded or spiral tubes. Some models include integral ballast and screw base which allows them to… More » |
| Context parameters |
Parameters beyond the control of designers that affect performance. Original Chapter Source: Daylighting Provided By: Kosta Papamichael / CLTC More » |
| Continuous dimming |
Control of the intensity of a light source without abrupt transitions between light levels. Original Chapter Source: Controls Provided By:… More » |
| Contrast |
Also known as luminance contrast, it is the relationship between the luminances of an object and its immediate background. [Source:… More » |
| Contrast magnitude |
The ratio between two adjacent luminance values. Original Chapter Source: Daylighting Provided By: Kosta Papamichael / CLTC More » |
| Contrast sensitivity |
The reciprocal of threshold luminance contrast. Original Chapter Source: Health & Performance Provided By: Peter Boyce More » |
| Control panel |
Cabinet-type enclosure containing a series of relays that receive low-voltage ON/OFF signals from another device and respond by switching the… More » |
| Control station |
Control stations enable aggregation of control of multiple dimmers into a single interface between the user and the controller (dimming… More » |
| Control zone |
A luminaire or group of luminaires controlled simultaneously by a single controller. Original Chapter Source: Controls Provided By: Craig DiLouie More » |
| Controller |
Generic term describing the device in a control system that electrically changes the output of the lighting system. Original Chapter… More » |
| Cooling loads |
The rate at which heat must be removed from a building or space to achieve thermal comfort for the occupants.… More » |
| Core body temperature |
The inner temperature of the body that is stabilized by thermoregulation. Original Chapter Source: Health & Performance Provided By: Peter… More » |
| Cornea |
The transparent front surface of the eye. Original Chapter Source: Health & Performance Provided By: Peter Boyce More » |
| Correlated color temperature |
A specification of the apparent color of a light source relative to the color appearance of an ideal incandescent source… More » |
| Cosine sensitivity |
The property of cosine corrected light meters in which the sensitivity to light decreases with the cosine of the angle… More » |
| Critical fusion frequency |
See Flicker fusion frequency. Original Chapter Source: Light & Vision Provided By: Heschong Mahone Group / Peter Boyce More » |
| Cylindrical illuminance |
The average illuminance on the surface of an infinitesimally small, vertical cylinder. Original Chapter Source: Light & Vision Provided By:… More » |
| DALI (Digital Addressable Lighting Interface) |
A marketing term developed by DALI-AG often used generically to describe a royalty-free, non-proprietary, two-way, open and interoperable digital protocol… More » |
| Daylight |
Light originating directly from the sun or direct sunlight that is scattered by the atmosphere. Original Chapter Source: Daylighting Provided… More » |
| Daylight harvesting |
The appropriate turning off of electric lighting systems during times at which sufficient daylight is available for visual tasks that… More » |
| Daylight zone |
Area of consistent and substantial daylight availability within a building, expressed in square feet. Also called the daylight area. Original… More » |
| Daylighting |
Lighting strategies that use the sky as a light source, while shielding or reflecting direct sunlight to avoid glare, heat… More » |
| Daylighting control |
Control strategy in which lighting is either switched OFF or dimmed when photosensor-measured incoming or task light levels rise above… More » |
| Demand charge |
Utility rate structure which charges based upon peak electric demand use during the billing month. Fee rate is in $/kW.… More » |
| Demand response |
Allows customers to bid into the power supply system by reducing building consumption during pre-defined peak load conditions. Original Chapter… More » |
| Design parameters |
Parameters that designers control to affect performance. Original Chapter Source: Daylighting Provided By: Kosta Papamichael / CLTC More » |
| Device Settings |
Document listing all adjustable lighting controls in a project, identifying them by individual space or space type, and then clearly… More » |
| Diabetic retinopathy |
A common cause of partial sight caused by chronic diabetes. The effect is to damage parts of the retina. The… More » |
| Dichroic coatings |
Optically-thin layers of metalic materials applied to the lens or glass envelopes of lamps to selectively reflect or transmit certain… More » |
| Dielectric |
Nonconducting substance. Original Chapter Source: Luminaires Provided By: Leslie North More » |
| Diffuse daylight |
Daylight not originating directly from the sun or from specular reflections of the sun. Original Chapter Source: Daylighting Provided By:… More » |
| Diffuse reflectance |
The ratio of the luminous flux reflected from a surface to the luminous flux incident on the surface. Original Chapter… More » |
| Dim |
The act of reducing light intensity. Original Chapter Source: Daylighting Provided By: Kosta Papamichael / CLTC More » |
| Dimmable ballast |
Fluorescent or HID ballast specially designed to provide the ability to adjust light output by modifying the lamp current. Original… More » |
| Dimmer |
A control device for varying the light output of lamps. Original Chapter Source: Controls Provided By: Craig DiLouie More » |
| Direct Glare |
Glare caused by a light source directly visible. Original Chapter Source: Design Considerations Provided By: Leslie North More » |
| Disability glare |
Glare that causes a deterioration in visual capabilities. Disability glare is caused by light being scattered in the eye, the… More » |
| Discharge lamps |
Electric light sources which produce light by passing electrical current through an ionized gas. Examples include neon lamps, xenon flash… More » |
| Discomfort glare |
Glare that causes discomfort. Discomfort glare does not necessarily cause a deterioration in visual capabilities. Original Chapter Source: Health &… More » |
| Distributed control |
Control strategy involving distribution of smaller control panels throughout a facility close to the loads they control. Original Chapter Source:… More » |
| Distributed intelligence |
Control system in which microprocessor intelligence and functionality is embedded in the control devices attached to the lighting network rather… More » |
| DMX512 |
A digital communications protocol most commonly used to control theatrical, stage and entertainment lighting and effects. Original Chapter Source: Controls… More » |
| Downlight |
A recessed luminaire usually using a point source, with a round or square aperture that projects light downward. Original Chapter… More » |
| Driver |
For light emitting diodes, a device that regulates the voltage and current powering the source. Original Chapter Source: Sources Provided… More » |
| Dual-loop photosensor |
Relatively new daylight harvesting technology combining open- and closed-loop photodiodes looking in different directions, with the result being greater accuracy… More » |
| Dual-switching |
A bilevel switching strategy involving dual-circuiting the inboard lamps separately from the outboard lamps in three-lamp luminaires, enabling three different… More » |
| Eccentricity |
The angle between the line of sight and the line from the eye to the position of the target. Original… More » |
| Eddy current |
Circulating flow of electrons (current) within a conductor which can create magnetic fields that oppose the change in magnetic field.… More » |
| Efficacy (luminous efficacy) |
Used in lighting as a measure of luminous efficiency where light (lumens) are compared to the electrical power (watts) used… More » |
| Efficiency |
A measure of the ability of a system to process energy (such as light) taking losses into account. Original Chapter… More » |
| Electricity delivery grid |
See power grid. Original Chapter Source: Policies & Programs Provided By: Craig DiLouie More » |
| Electrochromic |
Glass that has the ability to change its visible light transmittance with the application of an electric potential. Original Chapter… More » |
| Electrodes |
The structure that serves as the electric terminals at each end of electric discharge lamps. Original Chapter Source: Sources Provided… More » |
| Emission mix |
A coating that is place on fluorescent lamp electrodes to enhance electron production. Original Chapter Source: Sources Provided by: Erik… More » |
| Energy Use Intensity (EUI) |
Measure of energy efficiency of buildings expressed in kBTU per square foot. Original Chapter Source: Policies & Programs Provided by:… More » |
| Equivalent Sphere Illuminance (ESI) |
Visibility metric of how visible a specific target is under a proposed lighting system, as compared to the same target… More » |
| Erythema |
Reddening of the skin. There are many causes of erythema. Among them is excessive exposure to ultra-violet radiation leading ultimately… More » |
| Exitance |
The total quantity of light emitted by, reflected from, and transmitted through a surface into a complete hemisphere. It is… More » |
| Fenestration |
Any opening or arrangement of openings (normally filled with glazing media) for the admission of daylight, including any devices in… More » |
| Fixation |
A process by which the eye is held still so that the retinal image of an object remains on the… More » |
| Fixation point |
The position in the visual field that lies on the line of sight. The retinal image of the fixation point… More » |
| Fixed Wireless Control Network |
Network of wireless lighting control devices installed within range of a backbone of repeaters installed in set locations. Original Chapter… More » |
| Fixture efficacy |
The ration of light output of a fixture or luminaire to input power. Original Chapter Source: Sources Provided by: Erik… More » |
| Flicker fusion frequency |
The frequency at which a visual field repetitively oscillating in luminance appears not to be oscillating. The flicker fusion frequency… More » |
| Fluorescent Lamp |
A discharge lamp that produces light by means of electric current through low-pressure mercury gas. The arc produces ultraviolet energy… More » |
| Footcandle (fc) |
A measure of illuminance in lumens per square foot. One footcandle equals 10.76 lux, although for convenience 10 lux commonly… More » |
| Fossil fuel |
need to add definition More » |
| Fovea |
The central 2 degrees of the retina located on the line of sight. The fovea is structured so as to… More » |
| Fresnel lens |
A type of lens that achieves similar optical performance to conventional lenses while using considerably less material and within a… More » |
| Fuel cells |
Device that produces electricity from fuel (hydrogen) and an oxidant (oxygen) which react in the presence of a catalyst. Original… More » |
| GaN on GaN |
A new scientific innovation for LED technology is the ability to grow GaN crystals on its native GaN substrate (“GaN… More » |
| Ganglion cells |
A layer of the retina in which electrical signals from the cone and rod photoreceptors are combined and processed before… More » |
| General lighting |
Lighting designed to provide a substantially uniform level of illuminance throughout an area. Original Chapter Source: Luminaires Provided By: Franz… More » |
| Glare |
A source of light in the field of view that is much higher in brightness than the luminance to which… More » |
| Glare indices (Glare index) |
A method of predicting the presence of discomfort glare due to daylighting. Factors affecting the glare index include the size… More » |
| Glass |
An inorganic transparent material composed of silica (sand), soda (sodium carbonate), lime (calcium carbonate) and small quantities of alumina, boric… More » |
| Glaucoma |
A form of partial sight caused by excess pressure in the eye. The effect of the excess pressure is to… More » |
| Group relamping |
A method of conducting a planned replacement of a group of lamps prior to failure but near expected end of… More » |
| Halogen |
Lamps using a tungsten filament surrounded by halogen gas encapsulated in quartz, resulting in brighter, whiter light, higher efficiency, and… More » |
| Heliostat |
A system of mirrors that reflect the rays of the sun in a predetermined direction or towards a predetermined location.… More » |
| High intensity discharge (HID lamp) |
An electric discharge lamp in which the light is produced by an enclosed electrical arc using ionized gases operatiing at… More » |
| High-pressure sodium |
An electric lamp that produces light directly from an arc discharge under high pressure. Metal halide, high-pressure sodium, and mercury… More » |
| Horizontal illuminance |
Illuminance on a horizontal surface. Original Chapter Source: Daylighting Provided by: Kosta Papamichael / CLTC More » |
| HVAC |
Heating Ventilation and Air Condition Original Chapter Source: Policies & Programs More » |
| Hysteresis losses |
Losses from molecules in a transformer core resisting being magnetized and demagnetized by the alternating magnetic field. This resistance by… More » |
| IES |
Illuminating Engineering Society Original Chapter Source: Policies & Programs More » |
| Illuminance |
The area density of the luminous flux incident at a point on a surface. Units are Lumens per square foot… More » |
| Incandescent lamps |
Sources which produce light by utilizing long, thin filaments (usually made from tungsten) and heated to high temperatures (2700-3000 Kelvins… More » |
| Incandescent Reflector Lamp |
Incandescent/Halogen lamp fitted with an integral reflector used to focus light output in a desired direction and pattern. Original Chapter… More » |
| Induction Lamps |
A lamp that is power by an electromagnetic field rather than through lamp electrodes or direct electrical connections. Original Chapter… More » |
| Ingress protection (IP) rating |
International Protection (IP) rating system defined by International Standard IEC 60529, which classifies degrees of protection for electrical devices against… More » |
| Initial Cost (or First Cost or Initial Installed Cost) |
All the costs to purchase and install a fully functioning system. Original Chapter Source: Design Considerations Provided By: Leslie North More » |
| Input power |
Input power describes the amount of electric power, expressed in watts or kilowatts (1,000 watts), required to operate an electrical… More » |
| International Energy Conservation Code (IECC) |
The most commonly used residential energy code by states. Original Chapter Source: Daylighting Provided by: Kosta Papamichael / CLTC More » |
| Intrinsically photosensitive retinal ganglion cell (ipRGC) |
A ganglion cell in the retina which responds directly to incident light. The ipRGCs provide input to the human circadian… More » |
| Irradiance |
The incident radiant flux per unit area of a surface. Irradiance is measured in watts / square meter. Original Chapter… More » |
| Isofootcandle or Isolux |
Contour lines linking points of the same footcandle or lux value. Original Chapter Source: Design Considerations Provided By: Leslie North More » |
| Kelvin (K) |
The Kelvin scale is the basis of all temperature measurement, starting at the absolute zero, a theoretical condition at which… More » |
| L70 (subscript number) |
A lumen maintenance term that describes the amount of time that elapses before a light source's output has dropped to… More » |
| Lambertian |
Even cosine distribution. Original Chapter Source: Design Considerations Provided By: Leslie North More » |
| Lamp |
A radiant light source. Original Chapter Source: Sources Provided by: LRC - National Lighting Product Information Program (NLPIP) More » |
| Landolt ring |
A C-shaped target used to measure visual acuity and visual performance. The dimensions are such that the stoke width is… More » |
| LED array |
A collection of multiple LEDs mounted onto a substrate, usually a printed circuit board. The light output from the LED… More » |
| LED junction temperature (Tj) |
Temperature of the LED chip within an LED package. Tj is a critical parameter of LED performance. LED light output,… More » |
| LEED |
Leadership in Energy and Environmental Design (LEED) is an internationally recognized green building certification system, developed and managed by the… More » |
| Life cycle assessment (LCA) |
A framework for identifying and evaluating the environmental burdens associated with the life of materials associated with a product, from… More » |
| Life Cycle Cost-Effective |
An efficiency measure is considered Life Cycle Cost-Effective if savings in energy over the life of the efficiency measure outweigh… More » |
| Life-cycle cost analysis (LCCA) |
Economic method for assessing the total cost of facility system ownership taking into account all costs of acquiring, owning and… More » |
| Light |
Electro-magnetic radiation between the wavelength limits of 380 nm and 780 nm that stimulates the human visual system. Sometimes called… More » |
| Light pollution |
A term used two ways, meaning either the light that produces skyglow, the glowing atmosphere above populated areas that interferes… More » |
| Light to solar heat gain ratio |
The ratio between the visible light transmittance and the solar heat gain coefficient of a glazing. Original Chapter Source: Daylighting… More » |
| Light trespass |
Unwanted light that spills onto neighboring properties. Original Chapter Source: Luminaires Provided By: Naomi Miller More » |
| Light-Emitting Diode (LED) |
Light-emitting diodes (LEDs) are solid-state electronic devices that generate light via the transformation of electric energy to radiant energy within… More » |
| Lighting control |
General term referring to electrical devices and techniques necessary to provide the right amount of light where and when needed.… More » |
| Lighting Control Narrative |
This document is used to briefly define the context for lighting control systems (general project goals and goals for lighting… More » |
| Lighting Power Density (LPD) |
A measure of installed lighting power, expressed as Watts per square foot. Original Chapter Source: Policies & Programs More » |
| Line of sight |
The line from the eye to the fixation point. The retinal image of an object on the line of sight… More » |
| Load scheduling |
An energy-saving lighting control strategy for switching or dimming during hours when a building space is unoccupied or occupied by… More » |
| Load shedding |
A lighting control strategy for selectively reducing the output of luminaires on a temporary basis as a means to reduce… More » |
| Low-pressure sodium (LPS) lamp |
An electric discharge lamp where the arc tube operates at relatively low pressures and temperatures utilizing sodium vapor as the… More » |
| Lumen |
Unit of emitted light from a light source. More technically, a unit of luminous flux. Electromagnetic radiation weighted using the… More » |
| Lumen depreciation |
The decrease in lumen output that occurs as a lamp is operated, until failure. Also referred to as lamp lumen… More » |
| Lumen Maintenance |
Measure of how well a lamp maintains its light output over its operational life. Original Chapter Source: Sources Provided by:… More » |
| Lumen maintenance dimming |
Control strategy intended to save energy by varying energy consumption by maintaining a specified light level. Original Chapter Source: Controls… More » |
| Luminaire |
A complete lighting unit consisting of a lamp or lamps and ballast(s) (when applicable) together with the parts designed to… More » |
| Luminaire efficacy |
Efficacy of a light source or light source/auxiliary system modified by the efficiency of the luminaire in distributing light output… More » |
| Luminaire efficiency |
The percentage of the total light generated by the source that leaves the luminaire in all directions. Original Source: Manual… More » |
| Luminance |
The photometric quantity most closely associated with the perception of brightness, measured in units of luminous intensity (candelas) per unit… More » |
| Luminance contrast |
Luminance contrast quantifies the relative brightness of an object against its background. It can range from zero to one. The… More » |
| Luminance distribution |
The distribution of luminance arriving at a point from all surrounding directions. Original Chapter Source: Daylighting Provided by: Kosta Papamichael… More » |
| Luminance factor |
See specular reflectance. Original Chapter Source: Light & Vision Provided By: Heschong Mahone Group / Peter Boyce More » |
| Luminance ratios |
Ratios between the luminances. Original Chapter Source: Daylighting Provided by: Kosta Papamichael / CLTC More » |
| Luminous efficacy |
The expression of efficiency in converting power (watts) into light (lumens). Expressed as lumens per watt or lm/W. More » |
| Luminous flux |
Emitted light from a light source or a surface, measured in lumens. See Lumens. Original Chapter Source: Luminaires Provided By:… More » |
| Luminous intensity |
Quantity of light emitted from a light source or a surface in a given direction, measured in candelas. Original Chapter… More » |
| Lux (lx) |
A measure of illuminance in lumens per square meter. One lux equals 0.093 footcandle. Original Chapter Source: Daylighting Provided by:… More » |
| Macular degeneration |
A common cause of partial sight. The macular lies immediately above the central part of the retina. When it degenerates… More » |
| Maximum Allowable Junction Temperature |
The manufacturer rated temperature limit of the LED device. Junction temperatures above this value may lead to sudden catastrophic failure… More » |
| MCPCB (Metal Core Printed Circuit Boards) |
A type of printed circuit board that has the dielectric and copper layer laminated to a copper or aluminum core. … More » |
| Melatonin |
A hormone produced by the pineal gland at night. Melatonin circulates in the bloodstream as a messenger of time. Original… More » |
| Melatonin suppression |
The reduction in melatonin concentration following exposure to light. Original Chapter Source: Health & Performance Provided By: Peter Boyce More » |
| Mercury lamps |
A high intensity discharge (HID) lamp which utilizes mercury vapor at relatively high pressures and temperatures to generate light. Original… More » |
| Mercury starvation |
The state in which a fluorescent lamp does not have enough mercury vapor present, often resulting in a pinkish lamp.… More » |
| Mesh Wireless Control Network |
Network of wireless lighting control devices communicating as nodes in a network; a signal generated by one device is routed… More » |
| Mesopic vision |
The state of vision between photopic and scotopic vision in which both rod and cone photoreceptors are active. Conventionally, this… More » |
| Metal halide lamp |
A high intensity discharge (HID) lamp which utilizes mercury in combination with metal halide salts operating at relatively high pressures… More » |
| Minute of arc |
A measure of angle corresponding to one sixtieth of a degree. Original Chapter Source: Health & Performance Provided By: Peter… More » |
| Model lighting ordinance (MLO) |
Outdoor lighting ordinance designed to address light pollution issues. The MLO was developed jointly by the Illuminating Engineering Society of… More » |
| MR lamp |
A type of reflector lamp in which the reflector is made up of small individual reflecting surfaces. MR lamps are… More » |
| Multi-level switching |
A bilevel switching strategy involving dual-circuiting the inboard lamps separately from the outboard lamps in three-lamp luminaires, enabling three different… More » |
| Nadir |
The direction pointing directly below the fixture. It is the imaginary line running vertically from the center of the fixture… More » |
| Nanometer (nm) |
A subdivision of the SI unit meter equal to 10-9 meters. Original Chapter Source: Daylighting Provided by: Kosta Papamichael /… More » |
| Nonrenewable resources |
Sources of energy that cannot be renewed once they are depleted. The most common nonrenewable energy sources are oil, coal,… More » |
| Occupancy sensor |
A device that switches lights ON and OFF or dims and brightens them based on the presence or absence of… More » |
| Off-axis vision |
This occurs when the object to be seen appears off the line of sight, i.e., away from the fixation point.… More » |
| On-axis vision |
This occurs when the object to be seen occurs on the line of sight so the retinal image of the… More » |
| Open loop |
Photocontrol system that measures only daylight coming into the space, not actual light levels in the space. Original Chapter Source:… More » |
| Optical radiation |
Electro-magnetic radiation between the wavelength limits of 1 nm to 1 mm. Ultra-violet, visible and infrared radiation all fall within… More » |
| Overhead glare |
Glare caused by a light source located directly above the viewer. Original Chapter Source: Design Considerations Provided By: Leslie North More » |
| Override |
A switch or other method that can be used by occupants to ensure continuation of lighting when required outside of… More » |
| Owner Project Requirements |
Document produced during pre-design (programming) project phase, and refined over the course of the project, that clearly articulates owner requirements… More » |
| PAR lamp |
A type of reflector lamp with a Parabolic Aluminized Reflector. PAR lamps are sometimes called pressed glass reflector lamps because… More » |
| Parallel |
When lamps are wired to a ballast in parallel, if any of the connected lamps fail, the remaining lamps continue… More » |
| Passive infrared (PIR) |
Occupancy sensing method that detects occupancy by reacting to the movement of infrared heat energy emitted by people. Original Chapter… More » |
| PCB (Printed Circuit Board) |
Printed circuit boards are laminates of copper and dielectric polymer layers used to mount electronic components and carry electrical signals… More » |
| Peak demand |
Maximum electric demand load (kW) sustained for specified period (typically 15 minutes duration) . Original Chapter Source: Design Considerations Provided… More » |
| Peak electricity demand |
The highest amount of electrical power needed over a particular period of time. Original Chapter Source: Daylighting Provided by: Kosta… More » |
| Peak load |
See peak demand. Original Chapter Source: Policies & Programs Provided By: Craig DiLouie More » |
| Peak period |
See peak demand. Original Chapter Source: Policies & Programs Provided By: Craig DiLouie More » |
| Peak use |
See peak demand. Original Chapter Source: Policies & Programs Provided By: Craig DiLouie More » |
| Performance parameters |
Parameters used to evaluate performance. Original Chapter Source: Daylighting Provided by: Kosta Papamichael / CLTC More » |
| Performance Testing |
Project phase in which a contractor, under the supervision of the commissioning authority, inspects and tests installed systems to ensure… More » |
| Peripheral vision |
Visual activity involving off-axis vision is peripheral vision. Original Chapter Source: Health & Performance Provided By: Peter Boyce More » |
| Phase |
The timing of a repetitive oscillation at which it reaches an identifiable condition such as a maximum or a minimum.… More » |
| Photocell |
A light-sensitive device for measuring light intensity. (Also called a photosensor.) Original Chapter Source: Controls Provided By: Craig DiLouie More » |
| Photocontrols |
See daylighting control. Original Chapter Source: Policies & Programs Provided By: Craig DiLouie More » |
| Photokerititis |
Photochemical damage to the cornea caused by exposure to ultraviolet radiation. Original Chapter Source: Health & Performance Provided By: Peter… More » |
| Photoluminescence or "PL" |
A process in which a substance absorbs photons from some light source and, after a delay, re-radiates photons. The delay… More » |
| Photon |
An elementary particle, the basic unit of light. Original Chapter Source: Health & Performance Provided By: Peter Boyce More » |
| Photopic (photopic vision) |
The state of vision in which cone photoreceptors are dominant. Conventionally, photopic vision is taken to occur at adaptation luminances… More » |
| Photopigment |
A light-sensitive chemical contained in a photoreceptor. Original Chapter Source: Light & Vision Provided By: Heschong Mahone Group / Peter… More » |
| Photoreceptor |
A structure in the retina where light entering the eye is absorbed and converted into electrical signals. Original Chapter Source:… More » |
| Photoretinitis |
Photochemical damage to the retina caused by exposure to short wavelength visible light. Previously known as blue-light hazard. Original Chapter… More » |
| Photosensor |
A light-sensitive device for measuring light intensity. (Also called a photocell.) Original Chapter Source: Controls Provided By: Craig DiLouie More » |
| Phototransduction |
The process by which light is converted into electrical signals. Original Chapter Source: Health & Performance Provided By: Peter Boyce More » |
| Photovoltaics |
Field of technology related to the application of solar cells for conversion of daylight into electricity. Original Chapter Source: Luminaires… More » |
| Pigment epithelium |
The part of the eye immediately behind the retina. The pigment epithelium supplies nutrients to the retina and absorbs any… More » |
| Plasma Lighting |
An electrodeless lighting system consisting of a magnetron producing an electromagnetic field around a glass capsule inside an electrodeless lamp,… More » |
| Plenum |
In interior spaces, the Plenum is the space between the ceiling and either the next floor above or the roof.… More » |
| Polarization |
A process by which the electromagnetic field of light becomes oriented in particular directions. Original Chapter Source: Light & Vision… More » |
| Power factor |
The ratio of active power (in watts) to apparent power (in rms volt-amperes), power factor is a measure of how… More » |
| Power Grid |
The system of power production plants and distribution lines that deliver power to its end users. Original Chapter Source: Policies… More » |
| Power quality |
The degree to which current and voltage wave forms conform to a sinusoidal shape and are in synchronous phase with… More » |
| Power Supply (LED) |
An electronic device that transforms an incoming power supply to another form to be used by an electronic device. For… More » |
| Powerline carrier (PLC) |
Method of lighting control involving using line-voltage power wires as communication pathways for control signals. Original Chapter Source: Controls Provided… More » |
| Prismatic structures |
Faceted structures on a transparent material that modify the direction of the light traveling through that material. These structures usually… More » |
| Profile angle |
A characteristic of horizontal lines, such as the edges of an overhang, in reference to a point of interest, such… More » |
| Programmable-Start Ballast |
Advanced type of fluorescent rapid-start electronic ballast. Upon energizing of the circuit, the ballast preheats the lamp cathodes prior to… More » |
| Radiant exposure |
The product of the irradiance on a surface and the duration of exposure. Irradiance is measured in watts / square… More » |
| Radiant flux |
The rate of flow of electromagnetic radiation, measured in Watts. Original Chapter Source: Light & Vision Provided By: Heschong Mahone… More » |
| Rapid-start lamps |
A fluorescent lamp that requires its electrodes to be heated prior to starting, using a starter that is an integral… More » |
| Rare-earth (RE) phosphors |
A group of phosphors containing rare-earth elements. Rare-earth phosphors are used in fluorescent lamps to achieve high efficacy and better… More » |
| Receptive field |
The area of the retina to which a retinal ganglion cell is connected. Original Chapter Source: Light & Vision Provided… More » |
| Reference ballast |
A ballast that is built to a specific standard for the sole purpose of testing and characterizing lamps and other… More » |
| Reflected glare |
Glare caused by a reflection of a light source in an object within the field of view. Original Chapter Source:… More » |
| Reflection |
The change in direction of a light ray at the boundary between two media so that the ray returns into… More » |
| Reflector lamp ("R" lamp) |
Lamps made of blown or molded glass formed such that a parabilic or other shape is created which directs the… More » |
| Refraction |
The change in direction of a light ray when it enters a different medium. Original Chapter Source: Light & Vision… More » |
| Relative Photometry |
Photometry is the measurement of the properties of light, particularly intensity. Relative photometry, used for luminaires with conventional light sources,… More » |
| Relay |
Power-switching device that receives low-voltage ON/OFF signals from another device and responds by closing or opening the circuit to turn… More » |
| Retina |
The photosensitive surface at the back of the eye where photons of light are converted into electrical signals that are… More » |
| Retinal illumination |
The amount of light falling on the retina derived from the luminance of the scene being viewed and the area… More » |
| Retinal image |
The image of the outside world formed on the retina by the optical elements of the eye. The quality of… More » |
| Retinal irradiance |
The irradiance falling on the retina, measured in watts per square meter. Original Chapter Source: Health & Performance Provided By:… More » |
| Return on investment (ROI) |
Also known as Rate of Return is expressed in terms of the interest rate that makes the Present Worth of… More » |
| RoHS |
Restriction of Hazardous Substances Directive; a European Union directive dictating restrictions on a variety of hazardous substances (including mercury) that… More » |
| Room Cavity Ratio (RCR) |
Environmental factor used in lighting design calculations. Cavity defined by the luminaire plane, task plane and the vertical wall area… More » |
| Saturation |
A characteristic of the response to a stimulus in which increasingly large changes in the stimulus produce decreasingly small changes… More » |
| Scalar illuminance |
The average illuminance on the surface of an infinitesimally small sphere at a point – also called mean spherical illuminance.… More » |
| Scattering |
The change in direction of a light ray caused by an interaction with localized non-uniformities in a medium. Original Chapter… More » |
| Scene |
A dimming level that is intended to be repeatable with a push of a button. Original Chapter Source: Controls Provided… More » |
| Scheduling |
An energy-saving lighting control strategy for switching or dimming during hours when a building space is unoccupied or occupied by… More » |
| Scotopic (scotopic vision) |
The state of vision in which only rod photoreceptors are active. Conventionally, scotopic vision is taken to occur at adaptation… More » |
| Scotopic/Photopic Ratio |
The ratio of scotopic luminous flux to photopic luminous flux produced at a point by a light source or a… More » |
| Sequence of Operations |
Description of how a lighting control system responds to various inputs in a given space. Example: “The occupancy sensor will… More » |
| Series |
When lamps are wired to a ballast in series, if any of the connected lamps fail, all the lamps are… More » |
| Shading masks |
Parts of the sky dome that are blocked by exterior surfaces, such as the landscape, neighboring buildings and building-mounted shading… More » |
| Simple payback |
Method of economic evaluation expressed in units of time (the payback period) to recoup an investment based on the initial… More » |
| Size of detail |
For a visual stimulus, the size of detail is always expressed in terms of the angle subtended by the detail… More » |
| Skyglow |
The glowing atmosphere above populated areas that interferes with view of the night sky. Original Chapter Source: Luminaires Provided By:… More » |
| Skylights |
Apertures in the roof of a building that allow daylight into the interior. They are usually covered by a transparent… More » |
| Snapback |
The reversion of luminaires with CFLs back to incandescent light sources. Original Chapter Source: Sources Provided by: Erik Page More » |
| Solar Heat Gain Coefficient (SHGC) |
The Solar Heat Gain Coefficient (SHGC) measures how well a window blocks heat from sunlight. The SHGC is the fraction… More » |
| Solar radiation |
Electro-magnetic radiation emitted by the sun. This comprises infrared, visible, and ultraviolet light. Original Chapter Source: Daylighting Provided by: Kosta… More » |
| Solar spectrum |
The amount of radiation emitted in each wavelength that composes solar radiation. Original Chapter Source: Daylighting Provided by: Kosta Papamichael… More » |
| Solid angle |
The solid angle subtended by an object at a point is given by the area of the object divided by… More » |
| Solid state lighting (SSL) |
A form of lighting that uses semi-conductor materials to emit light, rather than using glowing filaments or gas-discharge sources. Original… More » |
| Source efficacy |
The ratio of light output of a light source to input power. Original Chapter Source: Sources Provided by: Erik Page More » |
| Spacing Criteria (SC) |
A multiplying factor calculated for a specific luminaire, which describes how far apart the luminaires can be spaced to deliver… More » |
| Spectral sensitivity |
The sensitivity of the effect of interest to wavelength. The effect of interest can be visual, e.g., brightness, or non-visual,… More » |
| Specular |
Mirror-like reflective properties where the angle of incidence equals the angle of reflectance. Original Chapter Source: Design Considerations Provided By:… More » |
| Specular reflection |
A mirror-like reflection in which the angle of incidence is equal to the angle of reflection. Original Chapter Source: Health… More » |
| Spot relamping |
A method of replacing lamps only after they have failed. Original Chapter Source: Sources Provided by: Erik Page More » |
| Standard 189.1 |
ASHRAE Standard 189.1, a reach code designed to improve on the efficiency of Standard 90.1, similar to the LEED system,… More » |
| Standard 90.1 |
ANSI/ASHRAE/IES Standard 90.1, the federally referenced energy code, originally developed by ASHRAE, and now revised and updated in collaboration with… More » |
| Step-dimming ballast |
A ballast that reduces light levels by one or more steps between full light output and OFF. Original Chapter Source:… More » |
| Steradian |
SI unit of solid angle. Original Chapter Source: Design Considerations Provided By: Leslie North More » |
| Sunlight |
need definition More » |
| Suprachiasmatic nuclei (SCN) |
The master clock of the human circadian system. Original Chapter Source: Health & Performance Provided By: Peter Boyce More » |
| Switch |
A control device that provides ON/OFF lighting control by mechanically closing or opening the circuit. Original Chapter Source: Controls Provided… More » |
| System efficacy |
Also referred to as relative system efficacy, system efficacy is a measurement of a system's ability to convert electricity into… More » |
| Systems Manual |
Document produced over the course of a project and delivered to the owner upon acceptance, which provides detailed information about… More » |
| T-5 |
A fluorescent lamp that is 5 eights in diameter. Original Chapter Source: Sources Provided by: Erik Page More » |
| T-8 |
A fluorescent lamp that is 8 eights in diameter. Original Chapter Source: Sources Provided by: Erik Page More » |
| Tandem Wiring |
Wiring scheme in which two or more luminaires share a single ballast, reducing installation and energy costs. Original Chapter Source:… More » |
| Task tuning |
A lighting control strategy in which the light output of a luminaire or group of luminaires can be adjusted by… More » |
| Taskplane |
The surface or area on which visual attention is placed. In an office space, the workplane is at desk height,… More » |
| Temporal modulation |
The temporal modulation of a repetitive oscillation is quantified by the formula M = (Lmax – Lmin) / (Lmax +… More » |
| Thermal discomfort |
Discomfort caused by excessive or insufficient heat transfer from the environment to the human body. Original Chapter Source: Daylighting Provided… More » |
| Thermal factor |
Thermal factor is a light loss factor that should be applied to a lighting design when application conditions imply ambient… More » |
| Thermal loads |
Heat that needs to be removed from or added to a space in order to make that space comfortable for… More » |
| Threshold limit values |
The amounts of optical radiation which it is believed normally healthy humans may be repeatedly exposed to, day after day,… More » |
| Thyristor |
A four-layered semiconductor used for power control, enabling ON/OFF switching and dimming using a method called phase angle control. While… More » |
| Time-clock |
A control device that switches or dims the lights at a set future time. The term is also used to… More » |
| Timer switch |
A control device that turns the lights in a single load switch leg OFF after a preset period of time… More » |
| Tinted glazings |
Glazings that are made of tinted glass, which has additives that cause it to have lower visible light transmittance than… More » |
| TIR (Total Internal Reflection) |
The point where the angle of incidence of the light ray to a refractive surface is greater than the critical… More » |
| Total harmonic distortion |
A measure of the degree to which a sinusoidal wave shape is distorted by harmonics, with higher values of THD… More » |
| Transmission Losses |
Decreases in delivered electricity from “primary” electricity generated due to inherent inefficiencies in the delivery grid. Original Chapter Source: Policies… More » |
| Transmittance |
Fraction of light that is transmitted by a certain thickness of material. Original Chapter Source: Daylighting Provided by: Kosta Papamichael… More » |
| Transparent |
The property of materials that allow light to be transmitted with negligible or no scattering. Original Chapter Source: Daylighting Provided… More » |
| Triac |
The triode alternating current switch, or triac, operates similarly to a thyristor but is typically designed to handle smaller loads… More » |
| Troffer |
The housing of a fluorescent luminaire, usually a recessed metal housing that looks like an inverted trough. Original Chapter Source:… More » |
| Troland |
The unit of measurement of retinal illumination. Original Chapter Source: Light & Vision Provided By: Heschong Mahone Group / Peter… More » |
| Tungsten-halogen lamps |
Incandescent lamps which utilize a halogen gas surrounding the filament to produce a recycling of the tungsten filament material back… More » |
| U-value |
The heat transfer coefficient of a building component and is the magnitude of heat flow through that component per unit… More » |
| Ultrasonic |
Occupancy sensing method that detects occupancy by transmitting ultrasonic energy throughout the space and measuring the return frequency. Original Chapter… More » |
| Underwriters Laboratories |
An independent non-profit, nongovernmental product safety certification organization, accredited by the US Occupational Safety & Health Administration (OSHA), the American… More » |
| Unified glare rating (UGR) |
Metric developed by the CIE intended to predict discomfort glare. Values range from 5 to 30 with the higher the… More » |
| User Training |
Part of the commissioning process for a building system, this step, which occurs at the end of the construction project… More » |
| USGBC |
United States Green Building Council Original Chapter Source: Policies & Programs More » |
| Vacancy sensor |
Term used to describe manual-ON occupancy sensors. Original Chapter Source: Controls Provided By: Craig DiLouie More » |
| VDT |
Video Display Terminal (computer monitor) Original Chapter Source: Design Considerations Provided By: Leslie North More » |
| Veiling reflections |
Specular reflections that appear on an object viewed and that partially or wholly obscure the detail by reducing luminance contrast… More » |
| Vertical illuminance |
Illuminance on a vertical surface. Original Chapter Source: Daylighting Provided by: Kosta Papamichael / CLTC More » |
| Visible Light Transmittance (VLT) |
Transmittance of a material for visible light. Original Chapter Source: Daylighting Provided by: Kosta Papamichael / CLTC More » |
| Visual acuity |
An angular measure of spatial discrimination between neighboring objects such as points or lines that can just be perceived to… More » |
| Visual cortex |
The part of the brain that receives signals from the eyes and which constructs a model of the outside world… More » |
| Visual field |
The angular area over which objects can be seen. For normal viewing, the visual field is limited by the obstructions… More » |
| Visual Impairment |
Functional loss of visual acuity, reduction of peripheral field detection, or reduced peak contrast sensitivity. Some causes are retinal degeneration,… More » |
| Visual performance |
The performance of a visual task measured in terms of speed and accuracy. Original Chapter Source: Health & Performance Provided… More » |
| Vitreous humor |
The transparent, jelly-like substance that fills the space between the lens and the retina in the eye. Original Chapter Source:… More » |
| Wallwasher |
A linear or point source luminaire that is designed to direct light toward a wall in order to light it… More » |
| Windows |
An opening in the vertical surfaces of the building envelope for the admission of daylight. Original Chapter Source: Daylighting Provided… More » |
| Workplane |
The surface or area on which visual attention is placed. In an office space, the workplane is at desk height,… More » |
| Zenith |
Direction pointing vertically upwards from any given point on earth. Original Chapter Source: Daylighting Provided by: Kosta Papamichael / CLTC More » |
| Zonal lumen summary table |
Element of luminaire photometric report typically presented in the manufacturer catalog sheet for the product. The table lists the luminaire's… More » |
|
