Headlamps and the Full Moon Standard
The Most Romantic Standard Ever
The full moon standard is a very simple benchmark test for manufacturers. It allows them to measure how long a headlamp can run on a fresh set of batteries. The standard goes back to the idea, that a clear full moon night provides enough light for the human eye to see properly. The actual brightness of such a night is always 0.25 Lux – almost everywhere on the globe.
Now, when you try to remember your last clear full moon night, you probably remember a decent amount of light. Bright enough to see things clearly. And you may agree that a clear full moon night is bright enough to find your way on a trail…without needing a headlamp.
Manufacturers seem to like the idea of using this natural benchmark for a low light scenario. So, they decided to use – or misuse(!) – the “full moon scenario” for their needs. As a reference for the minimum light output a headlamp should have.
A “full moon” testing procedure could be as follows: You load a product with a fresh set of batteries and turn it on. You let it shine until the product reaches the minimum benchmark of 0.25 Lux light output. That’s where you stop your watch to see how long the batteries have lasted. Hmmm… Sounds reasonable so far. But it’s not.
Instead, it only does two things. It produces enormous runtime hours. Plus, it makes customers believe that the minimum output of their product is bright enough to see as good as in a clear full moon night.
A Basic Misunderstanding of Light
We’re facing a big problem here. Because the full moon standard is based on massive misunderstanding of light and the perception of light in the human eye. What sounds like a useful standard at first, turns out to be very misleading for the customer.
Here is why: Talking about sunlight or moonlight, we’re talking about a “light source” which is enormously far away. So the light is hitting our planet in a wide straight beam of light. Equally and everywhere, as far as you can see. Looking around, you’re always looking at the same level of illumination.
Image above: This is how most of us remember a clear Full Moon Night
So, in a full moon night we’re looking at 0.25 Lux everywhere around us. On the trail, on the fields, on every obstacle and everywhere else. And since there is light, there’s also reflection. Meaning that every obstacle, field or trail is also reflecting light. Not much, but still enough to create an even smoother impression of brightness.
The human eye loves such constant light conditions. Our pupils have plenty of time to fully adopt. Unlike constantly needing to adjust between bright and dark areas. They open up as much as they can and they stay open. As a result we see even better. And that’s why we always remember a full moon night as a bright night.
This Small Spot of Moon Light Is Annoying
Now, please keep this beautiful bright “full moon night” impression in mind. We want to compare it to this random outdoor scenario: You’re out on the trails, your hike has taken longer than expected and it’s dark by now. The moon is far from shining bright. Actually, you cannot even see it through the clouds. Not enough, your headlamp is almost dying.
The remaining light is a tiny spot in front of you. A dim spot of maybe 0.25 Lux, not even the size of a bike wheel. Everything around you is dark and you’re looking at a tiny spot of moonlight only. How annoying!
And that’s the point already. A small spot of moonlight cannot be compared to any clear full moon night. Or any visual conditions in such a night. But that’s what this standard suggests, and that’s why we think it’s misleading. We think, 0.25 Lux out of a headlamp are nothing more that a drop of water in a desert. And therefore doesn’t qualify as a reference for minimum light output.
The Last Chance Light
In an emergency, you may be happy your headlamp is still producing 0.25 Lux of light. You may thank god there’s some light left – a kind of a “last chance light” which may still bring you home.
But such a scenario cannot explain why 0.25 Lux should count towards the “official” total runtime of a headlamp. Manufacturers should specify a more realistic benchmark for the end of light output. Just like the ANSI FL1 Standard recommends it: It suggests to stop runtime measurements when 10% of the initial light output are reached.
If any product keeps producing 0.25 Lux thereafter, that’s great and helpful in an emergency. But don’t make us believe 0.25 Lux would be useful in any normal situation.
Please note our experience with most headlamps: 70-90% of the manufacturers claimed total runtime usually happens with less than 10% of the initial brightness of the lamp. Thanks to the Full Moon Standard.
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