Bulb output degradation

Assuming a first-line bulb (not a cruddy Asian-made one), and assuming no reduced-voltage daytime running operation, lumen maintenance is around

90%. Reduced-voltage daytime running operation causes bulb output to drop much further even when the bulb is operated at full voltage.

The bigger difference is in the *type* of bulb. Ultra-high-efficacy bulbs produce more light than high-efficacy bulbs produce more light than standard bulbs produce more light than long-life bulbs produce more light than blue bulbs.

What kind of H7 did you take out of which headlamp in what kind of car? What kind did you put in?

DS

OK, that's a long-life/less-light bulb.

Actually, the VW DRLs are reduced-intensity low beam. The intensity reduction isn't very obvious to the naked eye, especially in the daytime, because low beam DRLs have to be run at at least 76 percent of normal voltage. But it's enough to increase and accelerate the light degradation with age.

Not only to long-life bulbs produce less light when new (as a result of the internal changes made to maximize life) but they live long enough to grow very dim.

DS