From Watts To Lumens...To Lux

Until recently, we chose light bulbs according to watts because the wattage of an incandescent bulbs correlated to its size.  The number of watts, however, was an expression of the amount of energy it used.

During the 1980s, halogen bulbs replaced incandescent bulbs in bike lights. Still, bike lights were rated by wattage.  That designation continued even after Light Emitting Diodes (LEDs) replaced incandescent and halogen bulbs about twenty years ago.

Since LEDs use so much less energy, watts aren't a useful way to measure a bike light.  Bike lights thus came to be rated in lumens, which a measure of their light output.  (One lumen equals one candle.)  However, Kryptonite, which has just introduced a new line of bike lights, argues that lumens don't tell the story:  While a lumen count tells us how much illumination a bike light emits, it doesn't measure the effectiveness of the beam.  We want a light that allows us to see or be seen, but doesn't blind someone driving in the opposite direction.

That is why Kryptonite is rating its lights by a new unit:  the lux, which measures the illumination of a surface at a specific distance. According to the company, this measurement takes into account the quality, rather than mere quantity, of light because it takes into account how the light is focused.

Note:  I have not seen Kryptonite's new lights, so please don't take this as an endorsement of them.  However, I use, and have used, their locks.  If their lights are as well-designed, I think they'll be very, very good.