Luminance classification of decorative luminaires with opal surfaces

In order to facilitate the selection of luminaires with luminous opal surfaces, Fagerhult has developed a classification system that documents the average luminance for this type of luminaire.

The affected luminaire types are pendant, ceiling and wall as well as any other luminaire with opal luminous surfaces. Luminance classification should be used as a reference to assess the desired luminaire in relation to the luminance of the surroundings and how they are experienced.

The luminance values documented in the tables have been measured square to the luminaire and make up an average value for the luminaire’s luminous surfaces. A luminaire range can be classified in several luminance classes depending on the output of the light source that the luminaire is fitted with.

Luminance class ¹⁾
A < 1000 cd/m² The luminaire has a low average luminance and can be used in rooms with high anti-glare requirements e.g. offices with ordinary monitor work.
B 1000–3500 cd/m² The luminaire has relatively low average luminance and can generally be used in most situations. Against a light background the risk of glare is small.
C 3500–5000 cd/m² The luminaire has a relatively high average luminance and should therefore be used in bright surroundings to avoid glare.
D > 5000 cd/m² The luminaire has a high average luminance. The risk of glare can be large even if the luminaire is used in very light surroundings. The luminaire should therefore be avoided in rooms within the normal field of vision.
Key to the table

¹⁾ If the luminaire’s luminance balance exceeds 4:1 this is denoted with the additional designation* – example B*. The luminance balance is defined here as Lmax / Laverage.


The surroundings can be regarded here as light if the average value of the background luminance exceeds 20 cd/m² within a normal field of vision of ±20 degrees from a horizontal visual plane.

In order for the background luminance to exceed 20 cd/m² , the average vertical illuminance should exceed approx. 75 lx against a light wall. Investigations show that the relationship between the luminaire’s average luminance and background luminance should not exceed 40:1.


Light measurement and calculation of documented table values

Luminaire’s average luminance (cd/m²) – calculated from the luminaire’s technical data.


I = the luminaire’s luminous intensity square to the luminaire’s luminous surface (cd).

Ap = luminaire’s projected luminous surface (m²).

Laverage = luminaire’s average luminous intensity (cd/m²).

The luminaire’s maximum surface luminous intensity (cd/m²) – measured using a luminance meter with a measurement angle of 1°.


A= With a measurement angle of 1° the projected surface equates to a diameter of 26 mm (500 mm²) at a distance of 1.5 m.

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