Originally Posted by randya
You can argue wattage all you want, but dynamo systems with halogen lamps are plenty bright for both being seen and illuminating the road. I could show you a 15 watt tube audio amplifier that would knock the socks off a solid state unit ostensibly rated at 10 times the wattage.
What "plenty" is for you I suppose you're best fit to say. As far as comparisons to other lights are concerned, the good headlamps for generator lights are about as bright as brighter caving headlamps. So, to my mind, they're very good be-seen lights, and mediocre seeing lights.
I say "mediocre", and not "bad", or "unuseable", just to be clear. I've got a halogen caving headlamp that's about as bright as an acquaintance's generator-driven halogen headlamp (she's got a Schmidt hub generator), and that headlamp is a serviceable backup. It's not great. I certainly can't see the road-- I mean really *see* it, as opposed to inferring and guessing about a lot of what's there-- making 20+ mph descents. But it's not bad, either. I can see *some* of the road, and well enough to travel comfortably at less than 15mph.
By comparison, the rechargeable battery halogen light systems are certainly brighter than generator powered lights. There's no question, for example, that a 13w halogen Light and Motion system is much brighter than the lamps powered by generator hubs. This is just a matter of easily observable fact; it's not a matter for debate. The poster I was responding to was asking precisely about this comparison, and it's not just fair but accurate to say that he will be losing a lot of light moving to a 3w halogen headlamp from what he's got now.
The primary advantage of a generator hub is its continuous provision of power, whenever light is needed. This is greatly convenient-- no worries lighting. It's also safer than running a risk of your batteries going dead, though that worry can be partly alleviated, of course, through proper battery maintenance and carrying a backup (each of which adds to the inconvenience of battery lighting, though). The cost of this convenience is greatly reduced light compared to comparably priced battery powered systems, and, as I said above, a larger speed cost than some people imagine to the rider, too.
But a generator might well recommend itself to someone. I don't say otherwise. I don't see why we shouldn't be clear about the drawbacks as well as the advantages, though.