ČSN EN IEC 62722-2-1 ed. 2

#Citace

3 Terms and definitions
3.3 useful life
$L_{x} B_{y}$
length of time until at maximum a percentage $y$ of a population of operating LED luminaires of the same type have degraded to the initial luminous flux emitted multiplied by the luminous flux maintenance factor $x$

3 Terms and definitions
3.4 median useful life
$L_{x}$
length of operating time during which a total of 50 % ( $B_{50}$ ) of a population of operating LED luminaires of the same type have flux degraded to the initial luminous flux emitted multiplied by the luminous flux maintenance factor $x$