faktor čistosti mora znašati med 0,90 in 0,98, faktor prepustnosti pa najmanj 0,78, pri čemer se te vrednosti nanašajo na svetlobo, ki jo oddaja žarilna nitka žarnice pri barvni temperaturi 2 800 K in na del steklenega balona žarnice, ki je v žarometu 48 ur delovala pri preskusni napetosti.
the purity factor shall be between 0 790 and 0 798, and the transmission factor shall be not less than 0 778 (1), the values being determined for light emitted by an electric lamp filament at a colour temperature of 2 800 K and on a fragment of a filament lamp glass envelope which has been used in a headlamp at its test voltage for 48 hours.