Bike light manufacturers can put any ‘Lumens rating’ on their product that they want. There is no governing body out there that states that they have to measure or be truthful about what they claim their light output to be. What many of them do is read the LED spec that they are using, get that LED’s max rating and multiply by the number of them that they are using, and voila, magic Lumen number.
The problem is that number is a best case and impossible number. The real output is somewhere below that. The reasons for lower output are:
- Heat dissipation – as the LED gets hot, it gets dimmer to protect itself
- Power source – if the power source is not at the perfect voltage, it gets dimmer
- Reflector light loss – the mirrors on glass on a light will result in some light loss
- LED Binning – all LEDs at birth are sorted for their brightness. So all LEDs of the same model are not equal
That’s why Mtbr and RoadBikeReview work so hard to demystify LED output. The ultimate test is using an integrating sphere to measure light output. This piece of equipment costs about $20,000- $100,000 to purchase and requires a trained technician to operate. Mtbr is using the integrating sphere of Light & Motion and Lezyne to measure Lumen output. We are present during all measurements and we will cross-check their work with each other.
Video: Lumen measuring process using an integrating sphere with Chris McCaslin.
As you can see, it is not a simple process and that is why so many light manufacturers do not measure their output. There are very few independent labs around this country too that can do this work.
We realize of course that Light & Motion is a manufacturer and they are testing competitors’ lights. But we have evaluated their process and were present during testing. Furthermore, we are double-sourcing by testing at another manufacturer called Lezyne and cross-checking their work. We have already compared four lights that they each measured and the results match up within 1-2%. Finally, this is just a piece of our lights testing and is supplemented by our own Mtbr Lux lab testing and light beam image data.
These Lumen readings were recorded 31 seconds after the light was turned on. This is according to the FL-1 Flashlight Standard that specifies Lumen measurements to be recorded 30 seconds after the light is turned on. The FL-1 Flashlight Standard was created so manufacturers have a standardized method of measuring lights and making claims such as brightness and waterproofing. Some light companies are using the FL-1 standard and are fighting for its use in the bike light industry. Learn more about the FL-1 Flashlight Standard here.
2014 Lumen Test Results
2014 Claimed vs Measured Lumens Graph
2014 Lumens per Dollar Graph
2014 Lumens per Gram Graph
2014 Lumen-Hour Graphs
The Lumen-hour graphs below shows how the light performs over the first three minutes of its battery cycle.