Bulb output degradation

Another bulb related question....

What is the degradation in light output as a bulb ages? I put a new H7 in
my car and I can see the difference from one side to the other.

 

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

 

The car is an 02 VW golf, I think it was an Sylvania/Osram 64210L H7 and
that's what I put in. The difference from one side to the other was obvious
when parked in front of a wall. I think the DRL on my car goes full
intensity low beam.

 

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