Originally Posted by
Thrasymachus
How bright are dynamo systems? For example, I just got a rechargeable battery powered
Light & Motion, Taz 800(lumens) at a steal for only $134 at TheClymb. I found that on the 400 lumen setting I could go downhill on the road on an unlit street at full speed and feel very safe doing so. I assume that using the full 800 lumens I could do the same offroad, but that will only give me 2 hours of battery life.
In the future I want to get a new bike and go car-free and have always wondered about dynamo set-ups.
I know many people, most notably Jan Heine of Bicycle Quarterly, who are very comfortable descending twisty mountain roads with a dyno light (He uses the EDELUX, which is a design from a few years ago)...
The lumens claim from battery lights is misleading. It is a measure of the light emitted by a source, which in the case of battery lights is shaped like a cone (like a flashlight). So much of the light emitted is use to illuminate the sky.
Lux is a measure of how much light per a given area. Most of the dyno light the measurement is from a distance in front of the light (10m? at a given speed). 40 lux is about the measure for a living room with lights on at night. Office building hallways are around 80 lux. This should indicate that the 40-70 lux common in dyno lights is more than sufficient for riding at night.