Lighting Glossary

Beam angle is the angle across which a luminaire's intensity falls to 50% of its peak, describing how concentrated or spread the o…

The candela is the **SI base unit of luminous intensity**: luminous flux emitted per unit solid angle in one specific direction. W…

CRI (Ra) quantifies how faithfully a light source renders object colors compared with a reference source, on a scale where 100 is …

CCT describes the color appearance of white light, in kelvin, by comparison to an ideal blackbody radiator. Lower values are warme…

The foot-candle is the imperial unit of illuminance used chiefly in North America: one lumen per square foot. One foot-candle equa…

Glare is the visual discomfort or loss of visibility caused when a bright source sits in the field of view against a darker backgr…

Illuminance is the density of luminous flux arriving at a surface, measured in **[lux](/resources/glossary/lux/)** (lumens per squ…

L70 is the operating time after which an LED product's light output is projected to fall to 70% of initial — the industry's standa…

Light trespass is light falling where it is not wanted — flood lighting spilling into bedroom windows, port lighting washing over …

The lumen is the SI unit of **luminous flux**: the total quantity of visible light a source emits in all directions, weighted by t…

Luminance is the luminous intensity leaving a surface per unit area in a given direction, measured in **candela per square metre (…

Luminous efficacy is the ratio of luminous flux delivered to electrical power consumed, expressed in lumens per watt. It is the he…

Lux is the SI unit of illuminance: **one lumen of luminous flux spread over one square metre of surface**. It is the number lighti…

Maintenance factor is the multiplier a lighting design applies to account for the light a system will lose over its service life —…

SDCM (Standard Deviation of Colour Matching) expresses chromaticity tolerance in MacAdam ellipse steps — how tightly the actual wh…

UGR is the CIE metric for discomfort glare from indoor lighting installations, computed from the luminance of each fixture toward …

Uniformity ratio describes how evenly light is spread across a surface, most commonly as U0 = minimum lux ÷ average lux over the c…

ANSI C136 is the American National Standards family covering roadway and area lighting equipment — the North American counterpart,…

ATEX refers to the EU legal framework for explosive atmospheres — chiefly Directive 2014/34/EU covering equipment placed on the EU…

CCC (China Compulsory Certification) is China's mandatory product certification for goods sold on the Chinese domestic market, cov…

CE marking is the manufacturer's declaration that a product meets all applicable EU directives — for LED luminaires principally th…

DLC (DesignLights Consortium) is a North American qualification programme whose **Qualified Products List (QPL)** gates most US an…

EN 13201 is the European road-lighting standard series, used worldwide as the reference for street lighting tenders. Part 1 select…

FCC rules govern electromagnetic interference for electronic products sold in the United States. LED luminaires fall under FCC Par…

GB/T 3836 is China's national standard series for electrical equipment in explosive atmospheres, aligned part-for-part with the in…

IEC 60079 is the international standard series for equipment used in explosive gas and dust atmospheres, defining the protection c…

IECEx is the international certification scheme that tests and certifies equipment directly against the IEC 60079 series, issuing …

The IK code (IEC 62262) rates an enclosure's resistance to mechanical impact, from IK00 to IK10 (20 joules — a 5 kg mass dropped f…

The IP code (IEC 60529) rates an enclosure's protection with **two digits: the first against solids, the second against liquids**.…

ISO 9001 is the international standard for quality management systems — certifying not a product but the way a factory runs: docum…

LM-79 is the IES-approved method for photometric and electrical testing of complete SSL (LED) products: total luminous flux, effic…

LM-80 is the IES method for measuring lumen maintenance of LED packages: chips are operated at controlled case temperatures and dr…

REACH is the EU's chemicals regulation (EC 1907/2006) — Registration, Evaluation, Authorisation and Restriction of Chemicals — and…

RoHS (Restriction of Hazardous Substances, Directive 2011/65/EU) restricts lead, mercury, cadmium, hexavalent chromium, PBB/PBDE f…

SASO is the Saudi Standards, Metrology and Quality Organization, and clearing customs into Saudi Arabia requires product and shipm…

An all-in-one solar street light integrates panel, LiFePO₄ battery, controller, LED array, and motion sensor into a single pole-to…

A canopy light is a low-profile, surface- or recess-mounted LED fixture for the ceilings of petrol station forecourts, drive-throu…

The cobra head is the classic roadway luminaire silhouette — a slim arm-mounted head whose curved profile resembles a cobra's hood…

An explosion-proof light is a luminaire certified for classified hazardous areas — refineries, chemical plants, mines, grain handl…

A high bay light is an industrial luminaire designed for mounting heights of roughly 6 metres and above — factories, warehouses, l…

High-mast lighting mounts **multiple high-output floodlights on a single mast of roughly 20–50 metres** to cover a large area from…

An LED flood light is a projector-style luminaire that throws a controlled broad beam onto areas, facades, yards, and fields from …

An LED street light is a pole-mounted roadway luminaire engineered to put uniform light on a carriageway with controlled glare — t…

A linear high bay is a rectangular LED fixture whose elongated emitting area suits it to aisle-structured spaces: warehouse rackin…

A portable work light is a rechargeable, self-contained LED unit built to bring task lighting where fixed fixtures cannot: constru…

Shoebox light is the North American term for the rectangular, flat-bottomed LED area luminaire that lights parking lots, campuses …

A solar flood light pairs a directional LED flood head with its own panel and battery, delivering aimed area light where mains pow…

Solar garden light is the umbrella term for small self-powered landscape fixtures — path stakes and bollards, wall and fence light…

A solar security camera light combines an LED area or street light, a surveillance camera and a solar power system in one pole-mou…

A split (or semi-integrated) solar street light separates the solar panel from the lamp head, connecting them by cable, with the b…

A stadium light is a high-power LED flood light engineered for sports venues: hundreds to well over a thousand watts, precise narr…

A tri-proof (vapor-tight) light is a sealed linear luminaire protected against the three enemies of ordinary fittings — water, dus…

The UFO high bay is the compact circular LED format that has become the default industrial high-ceiling fixture: a finned die-cast…

Vapor tight light is the North American name for what European catalogues call a tri-proof light: a fully gasketed linear LED fixt…

0–10V is the simplest widely deployed dimming interface: a two-wire analog control pair on the driver, where 10 V commands full ou…

The ambient temperature rating (Ta) is the range of surrounding air temperature within which a luminaire is designed to operate at…

Autonomy is the number of consecutive sunless nights a solar light can run on battery alone — its buffer against cloudy spells. A …

COB (chip-on-board) LEDs mount many bare diode dies directly onto a single substrate under one phosphor layer, creating a compact,…

DALI (Digital Addressable Lighting Interface, IEC 62386) is a two-wire digital protocol in which each driver is an addressable dev…

Die-casting injects molten aluminum alloy into steel molds under high pressure, producing luminaire housings that are simultaneous…

Combustible dusts — grain, flour, sugar, wood, coal, aluminium — explode too, and dust atmospheres get their own zone system: Zone…

The Equipment Protection Level is the final element of a modern Ex marking — Ga, Gb or Gc for gas atmospheres, Da, Db or Dc for du…

Ex d — the flameproof enclosure — is the classic explosion-protection concept, and it works in a way that surprises people the fir…

Flicker is rapid fluctuation in a light source's output, usually inherited from how the LED driver converts AC mains to DC current…

Gas groups rank explosive gases by how easily equipment can ignite them and how violently they explode, setting construction requi…

The heat sink is the thermal path that moves waste heat from the LED junction into the air — and thermal design, more than chip ch…

An IES file (IESNA LM-63 format, or the European LDT/EULUMDAT equivalent) is the digital photometric fingerprint of a luminaire: a…

Ex e — increased safety — protects by prevention rather than containment: the design eliminates sparks, arcs and hot spots in norm…

Junction temperature is the temperature at the LED chip's semiconductor junction — the single variable that most decides how long …

LED binning is the manufacturer's sorting of produced chips into narrow performance groups — flux bins, forward-voltage bins, and …

The LED driver is the power-conversion electronics that turn mains AC into the regulated DC current LEDs require — and it is the c…

LiFePO4 (lithium iron phosphate) is the battery chemistry that has become standard in quality solar street lights, displacing olde…

Solar panels on lighting products come mainly in two silicon types. Monocrystalline cells, cut from a single crystal, convert more…

An MPPT (maximum power point tracking) charge controller is the electronics between a solar panel and its battery that continuousl…

The NEMA receptacle (ANSI C136.41) is the twist-lock socket on top of North American-style street lights that accepts a photocell …

Peak sun hours express a site's daily solar energy as the equivalent number of hours at full-strength sunshine (1,000 W/m²). A loc…

A photocell is a light-sensitive switch that turns outdoor lighting on at dusk and off at dawn automatically, with no timer to dri…

A PIR (passive infrared) sensor detects the **moving heat signature** of a person or vehicle and tells the fixture to react — typi…

Power factor is the ratio of real power (watts) to apparent power (volt-amperes) drawn from the grid, from 0 to 1. A fixture with …

The salt spray (salt fog) test, standardised as ISO 9227 or ASTM B117, exposes a finished housing to a continuous atomised salt mi…

SMD (surface-mounted device) LEDs are discrete packaged chips — familiar package names include 2835, 3030, and 5730 — soldered in …

Surge protection defends LED drivers against voltage transients from lightning activity and grid switching, specified in kilovolts…

The temperature class in an Ex marking states the maximum surface temperature the equipment can reach under worst-case conditions,…

THD measures how much a driver's input current deviates from a pure sine wave, expressed as a percentage of the fundamental. Switc…

Zhaga Book 18 is the specification behind the small round socket seen on modern European street lights, standardising the mechanic…

Zones classify hazardous gas areas by how probable an explosive atmosphere is: Zone 0 — present continuously or for long periods (…