Table contains maximum admissible luminance values which can reflect off the screen from the user’s point of view. These maximum luminance values depend on varying criteria in the corresponding guidelines and can be gathered from table. The thresholds for average luminance according to EN 12464-1 apply to flat screens of the current state of the art. As measurements of real screens have shown, they are predominantly used in positive display mode and with an average background luminance between 140 cd/m2 and 180 cd/m2. For laptops, background luminance is mostly set to less than 100 cd/m2. Accordingly, the luminance thresholds for luminaires specified in table must be observed.
Luminance thresholds
Table 3.69: Recommended luminance values in rooms with VDU workstations at a maintained illuminance of 500 lx depending on screen polarity
In section "Lighting of workstations with Display Screen Equipment (DSE) including VDUs", EN 12464-1 explicitly states that some countries have additional requirements. In Germany, these are contained in DIN 5035-7. Hence, table also contains the maximum permissible luminance thresholds according to this standard.
In the UK, the Lighting Guide LG7 "Office Lighting" (2015 edition) also contains luminance thresholds for luminaires. These values must be applied according to the Health and Safety (Display Screen) Regulations in force in the UK. The values are also contained in table.
Maximum permissible luminance values for avoiding disturbing reflections on screens also depend on screen display polarity. In negative screen display mode (bright characters on a dark background), disturbing reflections are more perceptible than with positive screen displays (dark characters on a bright background).
EN 12464-1 and LG7 define luminance thresholds for luminaires – not for other luminous surfaces.
According to EN 12464-1, the luminance thresholds in table apply from a distribution angle of 65° from the vertical, and in the planes C0, C15 and C30 to C345 in 15° steps. The requirements apply to screens with an inclination of up to 15° and a screen diagonal of up to 48 cm (19'').
For screens with a larger screen diagonal and more pronounced inclination as well as screens with reflection-sensitive surfaces, particular measures must be taken, e.g.
utilising luminaires with low luminance directed towards the work surface,
uilisation of luminaires where specified average luminance values are also met at distribution angles below 65°, e.g. starting at 55°,
particular arrangements of luminaires in relation to the screen,
lighting concept "partial area-based lighting" (see also section "Lighting concepts").
Table 3.70: Luminance thresholds for luminaires capable of reflecting off the screen according to EN 12464-1 and luminance thresholds for luminaires and room surfaces capable of reflecting off the screen according to DIN 5035-7 as well as luminance thresholds for luminaires according to LG 7 (Great Britain)