Light density unit L is candela per square metre (cd/m²),
this unit includes the origin of the quantity, that is
intensity of the light emitted l per surface angle A, ε
angle. L=I/A*cos( ε).
In brief, light density provides with clarity of a
surface which emits light or of a heat source. The Sun
has a light density of approx. 1 Mrd. cd/m², discharge
lamps about 10.000 cd/m². In the Anglo-Saxon area, the
unit foot lambert (ftl) is also used to measure light
intensity. This unit is also displayed if you wish so.
1 ftl = (1/π) cd/ft² = 3,426 cd/m².