The last days we got several questions concerning the light performance of Magnic Microlights which mainly depends on speed, rim distance, good adjustment and also rim material.
Lumen vs Lux
Many backers asked for Lumen and Lux values so let's first explain what it means:
- Lumen (symbol: lm) is a measure of the total quantity of visible light emitted by a source. This means light emitted in all directions is measured. A single candle has ~10 lumen. Despite the same lumen value, lamps can have different brightness, since focused light is brighter to the observer than light radiated all around.
- Lux (symbol: lx) is a measure for "light per unit area" (how much light can be measured on a square meter in 1m distance?), so the direction and the distance are important: A candle has 1 lux in 1 m distance. Since light decreases quadratically with the distance the candle has just 0,01 lux in 10 m distance. If we are talking of the "lux value of a bike light" this is not 100% accurate and this means the value in "10 m distance from the lamp". In Germany a bicycle light needs to have at least 10 Lux for STVZO/traffic approval (beneath some other complex rules connected with light distribution, LED performance, battery vs generator power, full and low power mode, generator performance +bicycle speed and also lens characteristics ).
Magnic Microlights prototype frontlights which are mounted in 2mm rim distance emit ~70 Lumen (~35 Lumen per light) at 20 km/h bicycle speed with standard aluminium wheels. We expect that we can increase these values to ~100 lumen because magnet material and coil winding of the prototypes are not perfect.
It is very important to mount the generators parallel to the rim - which is very easy with Magnic Microlights as you can see in the images below:
With our current lenses this means ~12 lux in 10 m distance. The prototypes have standard lenses with circular beam which will be replaced by optimized custom lenses. In combination with optimized generators the final product will have ~20 lux (in 10 m distance) at 20 km/h (pair of front lights). This is less than super bright battery lights but sufficient to enlight the road well in absolute darkness. Even with our prototypes you can cycle comfortably in absolute darkness.
Light output increases with higher speed: At 40 km/h the Magnic Microlights deliver more than 30 lux which means good illumination for downhill passages.
The Magnic Light Team
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