Terminology | Techlumen

Luminous Flux (Φ) lumen (lm)

The total quantity of visible light emitted by a light source in all directions per unit time. This is the fundamental measure for comparing the light output of different sources.

1 lm = 1 cd · sr

60W incandescent bulb: ~800 lm
18W LED tube: ~2,000 lm
Industrial LED luminaire: 10,000-50,000 lm

Illuminance (E) lux (lx)

The amount of luminous flux incident on a surface per unit area. It determines how well a workspace or surface is illuminated.

E = Φ / A → lux = lm / m²

Office: 500 lux (EN 12464-1)
Warehouse: 100-200 lux
Detailed industrial work: 750-1000 lux
Street lighting at night: 10-20 lux

Luminous Intensity (I) candela (cd)

The luminous flux emitted in a specific direction per unit solid angle. It describes how “strong” the light is in a particular direction.

I = dΦ / dω

The candela is one of the seven SI base units.

Luminance (L) cd/m²

The luminous intensity emitted or reflected from a surface in a specific direction, divided by the apparent area of the surface. This is what the human eye perceives as “brightness.”

White computer screen: 100-300 cd/m²
Sun: ~1.6 × 10⁹ cd/m²
LED chip surface: 10⁵ – 10⁷ cd/m²

Luminous Efficacy lm/W

The ratio of luminous flux produced to the electrical power consumed. The most important indicator of a light source’s energy efficiency.

Incandescent lamp: 10-15 lm/W
Fluorescent: 60-80 lm/W
Economy LED: 80-100 lm/W
Professional LED: 120-150 lm/W
High-efficiency LED: 170-220 lm/W

                        Note: We distinguish between Chip Efficacy (LED chip efficiency) and System Efficacy (total luminaire efficiency including driver and optical losses).
                    

Beam Angle degrees (°)

The angle between two directions where the luminous intensity drops to 50% of the maximum value. It determines how “narrow” or “wide” the light beam is.

Very Narrow: <10° — Architectural lighting, accent
Narrow Spot: 10°-18° — Artwork illumination
Spot: 19°-25° — Product highlighting
Flood: 26°-40° — General lighting
Wide Flood: 41°-60° — Uniform coverage
Very Wide: >60° — Diffused lighting

LED Chip / Die

The semiconductor core that produces light. Modern LEDs use various chip technologies such as SMD (Surface Mounted Device), COB (Chip on Board), and CSP (Chip Scale Package).

SMD: Individual chips on PCB, flexible design
COB: Multiple chips on common surface, high luminous flux density
CSP: Extremely small size, high efficiency

Binning

The process of sorting LED chips into groups (bins) based on their characteristics: luminous flux, color coordinates, and forward voltage. Ensures uniformity in luminaires.

                        Practical importance: Tight binning (1-2 step) is essential for applications where color consistency is critical (retail, museums, hospitality).
                    

LED Rated Life hours (h)

The operating time until luminous flux drops to a specified percentage of the initial value (usually L70 or L80). LEDs don’t “burn out” like conventional lamps but gradually lose brightness.

Typical professional LED lifespan: 50,000-100,000 hours
Comparison: Incandescent 1,000h, Fluorescent 10,000-15,000h

LED Driver

The electronic device that converts mains AC power to regulated DC current suitable for LED operation. It determines the reliability and performance of the luminaire.

Constant Current (CC): Fixed current, variable voltage
Constant Voltage (CV): Fixed voltage (12V/24V/48V)
Programmable: Adjustable characteristics

Thermal Management

The heat dissipation system that maintains LED chip temperature at safe levels. Critical for lifespan and performance retention.

Tj (Junction Temperature): LED junction temperature, typically max 105-125°C
Tc (Case Temperature): Housing temperature
Ta (Ambient Temperature): Environmental temperature

Every 10°C increase in Tj reduces lifespan by approximately 50%.

Correlated Color Temperature (CCT) Kelvin (K)

The color appearance of emitted light, expressed in degrees Kelvin. It describes the “coolness” or “warmth” of white light with reference to the color of a heated black body.

2700K: Warm White — Ambiance, hospitality
3000K: Warm White — Residential, retail
4000K: Neutral White — Offices, commercial
5000K: Daylight — Industrial, outdoor areas
6500K: Cool White — Laboratories, operating rooms

                        Tunable White: Luminaires with adjustable color temperature (e.g., 2700K-6500K) for Human Centric Lighting applications.
                    

Color Rendering Index (CRI) Ra (0-100)

Measures a light source’s ability to accurately reveal object colors compared to natural light or a reference source. Calculated as the average of 8 color samples (R1-R8).

CRI <80: Low rendering — Industrial, storage spaces
CRI 80-89: Good rendering — Offices, general lighting
CRI 90-94: High rendering — Commercial, hospitality
CRI ≥95: Excellent rendering — Museums, galleries, medical

                        R9 (Deep Red): Critical metric for food lighting (meats, fruits), skin tones, and textiles. Always request R9 >50 for these applications.
                    

Color Consistency (SDCM – MacAdam Ellipses) steps

Measures color deviation between LEDs of the same type. MacAdam ellipses define regions in the color diagram where the human eye cannot distinguish differences.

1 SDCM: Indistinguishable — Laboratory level
2-3 SDCM: Barely perceptible difference — Premium LED
4-5 SDCM: Noticeable in direct comparison — Professional
>5 SDCM: Visible difference — Economy LED

Unified Glare Rating (UGR)

Evaluates discomfort caused by glare in interior spaces. Calculated based on luminaire luminance, viewing angles, and background.

UGR ≤16: Technical drawing, detailed work
UGR ≤19: Offices, reading, computer screens
UGR ≤22: Industrial spaces, construction
UGR ≤25: Corridors, warehouses
UGR ≤28: Low-demand areas

Flicker

Rapid variation in light intensity that can cause discomfort, eye strain, and headaches. Particularly important in spaces with screens or cameras.

Flicker Percentage: <3% for workspaces
Flicker Index: <0.1 for high quality
SVM (Stroboscopic Visibility Measure): <0.4 for safety with rotating machinery

                        IEEE PAR 1789 recommends flicker-free operation for spaces with prolonged occupancy.
                    

Operating Voltage Volt (V)

The electrical voltage at which the luminaire operates. We distinguish between mains voltage luminaires (220-240V AC) and low voltage (12V, 24V, 48V DC).

220-240V AC: Standard mains voltage in Europe
110-120V AC: North America, Japan
12/24/48V DC: LED strips, special applications

Wattage Watt (W)

The electrical power consumed by the luminaire during operation. Includes both LED and driver consumption.

Power Factor (PF)

The ratio of real (useful) power to apparent power. High PF means more efficient use of the electrical grid.

PF = P (W) / S (VA)

PF >0.95: Excellent — Required for large installations
PF 0.90-0.95: Very good — Professional luminaires
PF <0.90: Acceptable only for low wattages

Low PF increases grid losses and may result in utility surcharges.

Total Harmonic Distortion (THD) %

The percentage of current distortion due to harmonic frequencies. High THD can cause problems in the electrical grid.

THD <10%: Excellent — Required for sensitive applications
THD <20%: Acceptable — Compliant with EN 61000-3-2
THD >20%: Problematic — Filtering required

Insulation Class

The method of protection against electric shock according to international safety standards.

Class I: Metal enclosure with earth connection
Class II: Double insulation, no earth required (symbol: □)
Class III: Safety extra-low voltage (SELV, <50V AC)

Ingress Protection (IP Rating)

International classification system defining protection against dust and water ingress. Consists of two digits: the first for solids (0-6), the second for liquids (0-9).

First digit (solids):

0: No protection
1-4: Partial protection from objects
5: Dust protected (limited ingress)
6: Dust tight (complete protection)

Second digit (liquids):

0: No protection
4: Splash resistant
5: Water jet resistant
6: Powerful water jet resistant
7: Immersion up to 1m for 30 minutes
8: Continuous immersion (>1m)
9K: High pressure/temperature jets

                        Common ratings:

                        IP20: Indoor • IP44: Sheltered outdoor • IP65: Wet areas, outdoor • IP66: Industrial, wash-down • IP67: Underground, pools

Impact Resistance (IK Rating)

Scale from IK00 to IK10 defining the luminaire’s resistance to mechanical impacts, measured in Joules.

IK00-IK05: Low resistance — Protected indoor spaces
IK06-IK07: Medium resistance — Offices, commercial (1-2 Joules)
IK08: High resistance — Industrial, schools (5 Joules)
IK09: Very high — Public spaces (10 Joules)
IK10: Extreme resistance — Anti-vandal (20 Joules)

Operating Temperature °C

The ambient temperature range in which the luminaire can operate reliably.

Indoor: 0°C to +40°C
Outdoor: -20°C to +45°C
Cold storage: -40°C to +25°C
High temperature: +50°C to +65°C

Corrosion Resistance

The luminaire’s ability to withstand corrosive environments such as marine air, chemicals, or high humidity.

Anodized aluminum: Good resistance, economical
Stainless steel (AISI 304/316): High resistance
Polyester powder coating: Protection with GSB/Qualicoat certification
Salt Spray Test: Resistance testing per ISO 9227

DALI (Digital Addressable Lighting Interface)

Digital communication protocol for lighting that enables individual control of each luminaire. Each device has a unique address (0-63) and can be grouped into scenes.

DALI-1: Basic protocol, 64 addresses
DALI-2: Improved interoperability, sensors, emergency
D4i: Integrated sensor power supply, data logging

                        DALI advantages: Bidirectional communication, fault reporting, easy expansion, manufacturer independence.
                    

0-10V / 1-10V Dimming

Analog dimming system where signal voltage determines brightness. Simple, economical, widely adopted.

0-10V: Active signal, 0V = OFF
1-10V: Passive signal, 1V = minimum (typically 1-10%)

DMX512

Digital control protocol for theatrical and architectural lighting. Supports 512 channels per universe, ideal for dynamic RGB/RGBW lighting.

Phase Cut Dimming (Triac / Leading Edge / Trailing Edge)

Dimming by cutting the AC waveform phase. Uses existing wiring without additional control cables.

Leading Edge (Triac): Older technology, for resistive loads
Trailing Edge: Better suited for LED, smoother operation

                        Caution: Compatibility between dimmer and driver is required. Check minimum load requirements.
                    

Wireless Control (Bluetooth, Zigbee, Casambi)

Wireless protocols for lighting control without additional wiring. Ideal for renovations and flexible installations.

Bluetooth Mesh: Up to 32,000 devices, mesh network
Zigbee: Low power, mesh, smart home compatible
Casambi: Professional, easy installation, cloud

Emergency Lighting

System providing illumination during power failure. Distinguished as maintained (always on) and non-maintained (emergency only).

Self-contained: Integrated battery in each luminaire
Central battery: Central power supply system
Duration: Minimum 1-3 hours per EN 1838

LM-80 & TM-21

LED lifespan measurement and projection standards established by IESNA (Illuminating Engineering Society of North America).

LM-80: Standard for testing LED chip lumen maintenance over 6,000-10,000 hours of operation
TM-21: Method for calculating lifespan projection based on LM-80 data

                        TM-21 projection is limited to 6x the LM-80 test duration. For L70 >50,000h projection, LM-80 data of at least 10,000 hours is required.
                    

LLMF (Lamp Lumen Maintenance Factor)

Factor expressing the percentage of initial luminous flux retained after a specific operating time.

L70: 70% of initial luminous flux
L80: 80% of initial luminous flux
L90: 90% of initial luminous flux
B10: 10% of LEDs have fallen below the threshold

Example: L80/B10 >50,000h means after 50,000 hours, 90% of LEDs will maintain at least 80% of initial luminous flux.

BUG Rating (Backlight, Uplight, Glare)

Light distribution classification system for outdoor luminaires, evaluating light pollution and glare.

B (Backlight): Light behind the luminaire (0-5)
U (Uplight): Light toward the sky (0-5)
G (Glare): Glare at high angles (0-5)

                        Lower values = less light pollution. Many municipalities require BUG ratings for new street lighting installations.
                    

EN 12464

European standard defining lighting requirements for workplaces.

EN 12464-1: Indoor work places
EN 12464-2: Outdoor work places

Specifies minimum lighting levels (lux), UGR, CRI, and uniformity for each activity type.

CE Marking

Marking indicating compliance with European Union health and safety requirements. Mandatory for market placement.

Relevant directives for luminaires:

LVD (Low Voltage Directive) 2014/35/EU
EMC (Electromagnetic Compatibility) 2014/30/EU
RoHS (Restriction of Hazardous Substances) 2011/65/EU
ErP (Energy-related Products) 2009/125/EC

ENEC

Pan-European safety mark awarded by accredited bodies. Exceeds minimum CE requirements with stricter testing and production inspections.

EU Energy Label

EU energy classification label (A-G scale from 09/2021) enabling energy efficiency comparison of luminaires and lamps.

Basic Photometric Quantities