Technical information

521www.fagerhult.com • www.fagerhult.co.uk
Luminance classification
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 docu-
ments the average luminance for this type of luminaire.
The aected 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 meas-
ured 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.
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 L
max
/ L
average
.
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 horizon-
tal visual plane.
In order for the background luminance to exceed 20 cd/m² , the average vertical il-
luminance 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.
Luminance classes for luminaires with opal surfaces
Luminance
class
1)
Average
luminance
Considerations:
A < 1000 cd/m² The luminaire has a low average luminance and
can be used in rooms with high anti-glare require-
ments e.g. oces 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 lu-
minance 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.
Light measurement and calculation of documented table values
Luminaire’s average luminance (cd/m²) – calculated from the lumi-
naire’s technical data.
I = the luminaire’s luminous intensity square to the luminaire’s
luminous surface (cd).
A
p
= luminaire’s projected luminous surface (m²).
L
average
= 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
p
= With a measurement angle of 1° the pro-
jected surface equates to a diameter of 26 mm
(500 mm²) at a distance of 1.5 m.
L
ave
=
Globia luminaire. See the product page for luminance classification information.
Polar diagram cd/1000 lm
Luminance uniformity=L
max
/ L
average
Luminance meter
I
A
p
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