In the beginning man created the contraption, the bicycle.
And sheesh way back then, the earth was without form, and void; and darkness was upon the face of the deep.
And the spirit of companies saw there was a need for more bike "stuff".
And many companies said, Let there be lights: and there were lights. Sooooooooo many lights.
And the cyclists saw the lights, that it was good: and the cyclist said I need light in the darkness.
So why am I writing about lights? Because I spent a lot of buck$ for a Fenix L2D which I saw on a bike bud's bicycle cycling back in the darkness in Shark Valley Everglades Park. It's a pretty nifty light (info www.fenixlight.com/viewproduct.asp?id=44 here) and looking back, why did I buy it?
I didn't do any research.
It just looked cool and the light output was awesome. I bought it.
As a cyclist you know how MANY different types of lights are out there: Everything from a small LED mounted on your handlebar to see your cycloputer to a full dynamo powered light that could set you back a mortgage payment and maybe even invoke a divorce layer.
When I got the Fenix L2D I wanted to compare it to my Cayeye.
The Fenix says it has XYZ Lumens.
The Cateye says it gives out ABC Candlepower.
What? Lumens? Candlepower?
I wanted to find out how to compare lumens to candlepower.
I give up after reading the explanation below. I now just turn whichever light I've got on my bike or in my bike bag and cycle with the old golden car rule in a fog: Don't over cycle what you can't see.
That philosophy works really well on steep, winding downhills in the dark when you're bike light is shining where the bike is pointing instead of where the road is going.
Yup another kind of bike light: Helmet mounted. And ya better believe I use one on brevets.
Anyhow, here's why I gave up trying to compare my Fexix L2d, to my CatEye Opticube to my Bike Planet light.
Helpful: I wish all light companies had a light finder such as this one on the Bike Planet page planetbike.com/page/learn/lightfinder/info/ color=black>(From theledlight.com )
The lumen/candle ummm..explanation for your reading pleasure
Lumens, Illuminance, Foot-candles and bright shiny beads….
In defining how bright something is, we have two things to consider.
1. How bright it is at the source- How Bright is that light?
2. How much light is falling on something a certain distance away from the light.
Lets' do some definitions now……
We're in America, so we are going to talk about units of measurement that concern distance in feet and inches. So, we will use some terms that folks in Europe don't use. We're going to talk about "foot-candles".
This one's simple. Get a birthday cake candle. Get a ruler. Stick the candle on one end of the ruler. Light the candle. Turn out the lights. Sing Happy Birthday to Doc. It was his 47th on the 23rd. OK, quiet down. Enough of that nonsense. One foot-candle of light is the amount of light that birthday cake candle generates one foot away.
That's a neat unit of measurement. Why? Say you have a lamp. You are told it produces 100 foot candles of light. That means at one foot from the lamp, you will receive 100 foot candles of light.
But here's where it gets tricky. The further away you move the light from what you want to illuminate, the less bright the light seems! If you measure it at the light, it's just as bright. But when you measure at the object you want illuminated, there is less light! A Physics teacher is going to tell you that light measured on an object is INVERSELY PROPORTIONAL to the distance the object is from the light source. That's a very scientific and math rich way of saying, the closer you are to the light bulb, the brighter that bulb is. Or, think of it this way. You can't change how much light comes out of your light bulb. So, to make more light on an object, you have to either move the light closer, or add more lights.
Now, lets get to LUMENS.
A LUMEN is a unit of measurement of light. It measures light much the same way. Remember, a foot-candle is how bright the light is one foot away from the source. A lumen is a way of measuring how much light gets to what you want to light! A LUMEN is equal to one foot-candle falling on one square foot of area.
So, if we take your candle and ruler, lets place a book at the opposite end from the candle. We'd have a bit of a light up if we put the book right next to the candle, you know. If that book happens to be one foot by one foot, it's one square foot. Ok, got the math done there. Now, all the light falling on that book, one foot away from your candle equals both…….1 foot candle AND one LUMEN!
Pretend you're an old photographer, like O. Winston Link, or Ansel Adams. These two gods of black and white photography (and a print made by either can fetch quite a hefty sum of money these days) used a device called a light meter to help them judge their exposure. (There is another way of judging exposure-that's when someone whispers in our ear at a cocktail party, "You silly twit, your fly's come undone!").
All this brings back two points. Well, three.
The first point is if we measure the output of a light at the source that gives us one thing.
The second point is that we use an entirely different unit of measure if we are measuring the results of that light's output.
The third point is the instructor is right off his trolley, isn't he?
Now back to the book at the end of the ruler.
We've measured two different things. We have a unit of measure for how much light is produced. We Yankees express that as a foot-candle. Being lazy, we use it all over the
place.
More Confusion! Candlepower!
Candlepower is a way of measuring how much light is produced by a light bulb, LED or by striking an arc in a Carbon-Arc spotlight. Is it a measure of how much light falls upon an object some distance away? No. That's illuminance. Is it a measure of how well we see an object that is illuminated by that light source? No. That's something all together different, and we are not going there!
I gave up. The rest of the article is even more confusing as were other websites.
Conclusion: Whatever light you want for your bike? Make sure there's some place you can test it to make sure it does what you think it'll do.
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