Lumen and lux; two different measurement methods
Lumen and Lux are both measurement units to visualize the strength of a light. But what is it and how does it work?
To start understand Lumen and Lux better we first have to start with the unit Candela (cd). With this term an amount of light from a lightsource (in this case your bicycle light) is shown independent of which way the light is emitted.
Lumen (lm) is all the light emitted from your lamp independet of which direction the light shines to. It's a so called photometric unit, this mean it takes in account the human eye. Does the light has the same amount of Watt but a different colour than the human eye imprints this as a different amount of Lumen.
BBB always measures there bicylces lights in lumen (not just the LED). We do this because the lumen might be higher or lower than the LED. Why? Because the LED must first pass a lens before it shines on the road. The worth of our lamps is this way the most honest.
The next unit is lux (lx). This unit stands for the amount of light (lumen) hits the surface (the road for example). This is unit is probably the most valuable because in the end you want to know what you can see 1 meter in front of you or how much light there will be in 10 meters.
Lumen and Lux in real life
When we developed the Strike we didn't just want to show the amount of lumen and boost this, but mainly wanted to create a complete lamp.
Below you can see the simularities and differences of the Strike 300 and Strike 500.
Both lamps give 28 Lux on a distance of 10 meters. They are both evenly bright. The Strike 500 got 200 lumen more light than the Strike 300. The Strike 500 also shines on a wider area which it uses the 200 extra lumens for.
Why didn’t we choose to use the same lens for both lights?
That’s because the human eye adapts to light. When there’s a lot of light, the pupil becomes smaller. With less light, the pupil becomes bigger. With a narrow bundle that’s very bright, the pupil becomes smaller, resulting in everything outside of your bundle becoming ‘invisible’. Because it’s outside the reach of your small pupil.
A logic question now would be to ask if every light than has to produce 28 lux on a distance of 10 meters. But that’s not the case. The keyword in developing lights is ‘balance’. As a designer of these products you constantly have to keep in mind that the light has to match the needs of each user. A helmet light has to create more of a hotspot, while a light on your handlebar has to have a wider bundle. And a light used on the road has to be about visibility. Each light has its own specific needs and goals.
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