Originally Posted by
ItsJustMe
How do you get a decent lighting system if you only have 3 watts to deal with? I run 5 watts just on my tail, and I certainly would not be willing to reduce that. Even with an efficient shaped beam I'd think you'd want at least 3 watts up front as well. My current light draws 8.5 watts, I imagine a shaped beam could get that down to 5 and still seem reasonable, but I'd think 10 watts would be a minimal amount of light I'd want to commute with in total.
Watts are a measure of power consumption, not of light output. Using watts to compare light output works only in an apples to apples situation.
If you're using watts to refer to light output, then I'm guessing you're using incandescents of some sort? (Halogens are also incandescent.) Remember that incandesents are very, very, inefficient. It helps to think of them as heaters that give off light as a waste product. Most of the power consumption goes into heating the filament, in much the same way as tube amps use most of their power to heat the tubes.
My first real light was a 10-watt NiteRider TrailRat halogen. Its light output was roughly equivalent to the pair of 200-lumen DiNotte 200-L-AA lights I replaced it with. They draw less than three watts each.
The current crop of LEDs are very efficient. Both my dynamo lights are easily 2x to 3x brighter than that pair of 200-lumen DiNottes, so, their 2.4 watts of power consumption is producing light output easily in excess of a 10 watt halogen--at least judging by my old eyes and memory.
The German lights all rate their output in lux, which is a measure of how much light actually falls on a specific target at a specific distance. It's a much better comparison than lumens, which is a raw measure of light output, not necessarily what ends up on the road.
Same goes for taillights, BTW. The pair of LEDs in my B&M Toplight Line Brake Plus draw a half-watt together, but are easily visible in daytime. This past summer I chased a bike on a sunny day to find out what taillight he was using in the daytime--a B&M Toplight Line Brake Plus. That's why I bought one.