A local Retro-Modern bike shop in West Seattle.    RideYourBike.com    

Volts (V), Amperes (A) and Watts (W) are all units of electricity.

V = W / A

A = W / V

W = V x A

Everyone knows how bright a 100 watt light bulb looks. However, watts aren't a good way to tell the brightness of a light source. Most street lights are 100 watts for example.
Bulb quality, material, the inert gasses inside the bulb (Krypton or Halogen), reflector and lenses all contribute to light output. The units Lumen, Lux and Foot-Candle are used to determine actual brightness. You could purchase a Lux Meter or just come into our shop and try out the lights in person. Many of the new LED lights are amazingly bright.
It is our opinion that many bike lights are TOO BRIGHT! Especially for trail use, where bikes come at you head-on.
Our staff commutes by bike all year long, so we have first-hand experience of what works.

Dynamo Lighting Links