Originally Posted by
noglider
I agree with your reason that parabolic reflectors and LED bulbs don't work well together. I'm asking you to clarify your point about LEDs optimized for 3-watt input. It appears that you are saying that the 1.8-watt output may be insufficient. Am I correct?
Yes, that is correct in some way, but I'm pretty sure it is incomplete. You'd be better off having it explained by someone who understands electricity better than i. Sheldon Brown has probably already f done so.
I do know that in Europe, where every bike has a sidewall dynamo, they sell 0.6w bulbs for the tail light and 2.4w bulbs for the headlight. It is common knowledge that if you burn out your tail light you must replace it immediately lest you overpower your head light bulb and fry that as well. I don't know if this is true. At any rate, those 2.4w bulbs are readily available and appear to fit Sturmey Archer lamps fine, but they produce a very weak light.