Industry glossary

Colour Rendering Index
Indicated as CRI on a scale from 0 to 100 and is a measure of a light source’s ability to reproduce colours.

DALI (Digital Addressable Lighting Interface)
A standardised protocol for digital control.

Failure fraction – Fy
The failure of fraction at nominal lifetime and is given in %. For example, at 15% failures, a factor of F15 is stated.

IP class
Specifies the degree of protection against access to live electrical parts and how waterproof and dustproof the fittings are. Stated as IP followed by two digits, e.g. IP23.

LED
(Light-Emitting Diode) is a semiconductor light source. LED lights have long lifespans and high energy efficiency. The light is formed by electroluminescence.

LEED
(Leadership in Energy and Environmental Design) is an international system for environmental certification for buildings. The certification focuses on reducing the use of resources such as land, water, energy and building materials.

Lighting Europe
The European trade association for luminaire and light source manufacturers.

LLMF (Lamp Lumen Maintenance Factor)
The light source’s maintained luminous flux at any given time.

LMF (Luminaire Maintenance Factor)
Specifies the luminaire’s pollution degree for a number of burning hours.

LSF (Lamp Survival Factor)
Specifies the number of light sources that still shine in a facility at any given time. (Expected shortfall of high quality LED can be assumed negligible and this factor becomes 1.0.)

Luminaire Luminous Efficacy
Defined as the ratio between luminaire luminous flux and luminaire power of an LED luminaire and stated in lumens per watt (lm / W).

Luminaire Luminous Flux
The total light output in lumens (lm) that a luminaire emits.

Luminaire power
Stated in watts (W) and is the total system power for a luminaire.

Luminance
Indicates how bright a surface is dependent on the light reflected from an object in a specific direction. Measured in candelas per m2 (cd/m2).

Luminous efficiency
Measurements of a light source efficiency and is calculated as the luminous flux divided by the power the light source consumes (wattage). Measured in lumens per watt (lm / W).

Luminous Flux
The amount of visible light emitted from a light source. Measured in lumens (lm).

Luminous Intensity
Specifies the amount of light that radiates in a certain direction. Measured in Candela (cd).

Luminous Intensity Distribution: Measured according to the CIE standard and stated in cd / 1,000 lm. Reported in the table or with polar plot.

MF (Maintenance factor)
The ratio between maintained illuminance and initial illuminance.

Nominal lifetime (Rated life)
Defined as the number of burning hours after which a given part of the initial light output remains. Today, life expectancy is given as the number of hours when 70% of the initial luminous flux remains and is designated as L70.

OLED
Abbreviation of Organic Light Emitting Diode.

PWM (Pulse Width Modulation)
A technique for light control with pulse width modulation recommended for LED.

Ra
An index that indicates light sources’ ability to render colours. Given on a scale from 0 to 100 where 100 indicates perfect colour reproduction.

RGB technique
A technique whereby mixing red, green and blue light can create white light or coloured light of a user’s choice.

UGR (Unified Glare Rating)
An international method developed by CIE to calculate an index of discomfort glare.

ZHAGA
An open consortium with the purpose of developing industry standards for LED components.