Light is a core area in the electrician's trade. Here are the photometric quantities (lumen, lux, candela, luminance), colour temperature and colour rendering, glare (UGR), lighting requirements after DS/EN 12464-1, emergency lighting after DS/EN 1838 and modern light control with DALI — plus the lumen method worked through.
Introduction
Good lighting is not just about having »enough light«. An electrician must be able to distinguish the photometric quantities from each other, dimension according to workplace requirements, avoid glare and install both emergency and control systems. A wrong choice of fixture or insufficient lighting intensity gives poor working conditions, errors and fatigue — too much gives glare and wasted energy.
The photometric quantities
Four basic quantities must be kept separate. Luminous flux is the total amount of light a source emits; illuminance is how much lands on a surface; luminance is how bright a surface appears when you look at it.
| Size | Symbol / unit | Means |
|---|---|---|
| Light flux | Φ / lumen (lm) | The total amount of light the source emits in all directions |
| Luminous intensity | I / candela (cd) | Light flux in a specific direction (lm per solid angle) |
| Illumination | E / lux (lx) | Lysstrøm pr. m² på en flade — 1 lx = 1 lm/m² |
| Luminance | L / cd/m² | The surface's "lightness" seen by the eye — what causes glare |
Colour temperature and colour rendering
Colour temperature (measured in kelvin, K) describes the tone of light — from warm yellowish to cool bluish. Colour rendering (Ra index, also called CRI) describes how natural colours appear in light, on a scale up to 100.
| Colour temperature | Tone | Typical use |
|---|---|---|
| < 3300 K | Warm white | Housing, cosiness, restaurant |
| 3300–5300 K | Neutral / white | Office, school, industry |
| > 5300 K | Cold / daylight | Precision work, hospital, control |
For most workplaces, DS/EN 12464-1 requires a colour rendering index of at least Ra 80, and where colour assessment is important (painting, printing, textiles) even higher. A low Ra makes colours look dull and wrong, even if the lux level is high.
Glare — UGR
Blænding opstår, når der er for stor luminansforskel i synsfeltet — en for lys lampe mod et mørkt loft. Direkte blænding vurderes med UGR-metoden (Unified Glare Rating), hvor et lavere tal er bedre. DS/EN 12464-1 sætter en øvre UGR-grænse for hver opgavetype: typisk UGR ≤ 19 for kontor- og læsearbejde, ≤ 16 hvor der stilles skærpede krav (fx teknisk tegning), og op til ≤ 25 for grovere arbejde. Refleksblænding fra skærme og blanke flader håndteres ved armaturvalg og placering.
Lighting requirements per DS/EN 12464-1
DS/EN 12464-1 (Light and lighting — lighting at indoor workplaces) specifies a maintained illuminance (Em) for each task type. 'Maintained' means the minimum value the system must deliver throughout its lifetime — in other words AFTER light sources age and accumulate dust. Extract of guideline requirements (verify against current edition, 2021):
| Area / task | Em (maintained) | UGR limit (recommended) |
|---|---|---|
| Traffic and pedestrian areas | 100 lux | 28 |
| Stairs | 100–150 lux | 25 |
| Canteen / break room | 200 lux | 22 |
| Archive, storage (shelves) | 200 lux | — |
| Office: writing, reading, IT | 500 lux | 19 |
| Technical drawing | 750 lux | 16 |
| Fine assembly / precision work | 750–1000 lux | 19 |
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