I went out last sunday for a ride early morning at 06:30am and was surprised by the low efficiency of the light. At first, I even thought the lamp was out of order as the visibility was equivalent to the one you have after a hangover....
So I am trying an alternative and plugged a LED bulb for 20 €.
before with original lamp :

after installing the led (plug and play):

not promoting anything, but if you are interested, the led can be found on auxito.com
cheers,
Sergio