Originally Posted by
cyccommute
I agree that it's subjective but I come at it from a different angle. An unlit country road? I could ride it with a fairly weak light without issue. In the city? Every possible lumen I can hang on me 'cause I'm competing with a huge quantity and variety of other light sources. I don't want to get lost in that ocean

Well put. The less ambient light, the less light I need to see by, and the more ambient light, the brighter my headlights need to be.