Pursuant to DIN 5040, Parts 1 and 2, luminaires can be classified by their luminous flux distribution, among other things, for various lighting applications. This luminaire classification gives a rough guide to the Beam Pattern of a given luminaire. The code used comprises a letter and two numbers. The letter relates to the proportion of luminous flux beamed downwards and/or upwards in the interior. The numbers indicate the percentage of lower and upper hemispherical luminous flux.
The code B63, for example, is to be interpreted as follows :
B Primarily direct light with 60-90% lower and 10-40% upper hemispherical luminous flux
6 70 - 100% of lower hemispherical luminous flux reaches the work plane
3 70 - 90% of upper hemispherical luminous flux reaches the ceiling