What Are Lumens?
Lumens are a measure of the total light generated from a source. It is described as being the total amount, or volume of light being delivered from a light source such as a flashlight. A lumen is measured as one candlepower. A 2,500 lumen flashlight will with an output of 2,500 candlepower.Lets use your garden hose as an example. Open the faucet feeding to the maximum level. Let\’s assume the total output of water flowing out of the faucet is 10 gallons per minute.
Compare that to our 2,500-lumen torch. At the highest battery strength, the highest output is 2,500 candlepower.We can set the outlet as a close, strong stream for washing dirt of a car, or as a wide pattern suitable for sprinkling the garden. The intensity between the two is different, but that water from the outlet is still open to 10 gallons every minute.But does the flashlight come with a nozzle, like a hose? Yes, it does. It\’s called a lens. The lens focuses the light. It can be focused into a narrow, high beam or opened up into a wide, dimmer beam. But the result is always the same: 2,500 lumens. The battery is not really dependant, but AA flashlights are the most popular for good reason: read more.
So when you purchase a flashlight, and the number of lumens is touted as a measurement of the flashlight\’s brightness, you know that is not necessarily true. Intensity depends on the kind of lens that is already on the flashlight. Is it a narrowly focused lens or a broadly concentrated lens? Some flashlights feature a movable lens so that the focus of the light can be changed from narrow to broad, but it does not alter the full total output, the number of lumens.
Result vs Radiance
So there are two things to measure on a flashlight, aren\’t there? Lumens, which is the output, and the measurement of the energy of the light, called radiance. It is a dimension of the effect of the light on its target.Radiance is the power, strength or intensity with which the light hits an object. Again, compare it to the water hose. A wide stream will break something fragile, and a close concentrated beam of light is strong enough to harm a human eye. This power or power of the light is its radiance.
Whenever we purchase flashlights, what we are interested in is the radiance of the light. This has more to do with the lens of the light than it can the lumens or the total result of the flashlight.Now, common sense tells us that if we open water valve fully, there is more water for the nozzle to work with and focus. Less water gives the nozzle less drinking water to target, so there is a relationship between output and power, but the nozzle, or in the case of a flashlight, the lens, is required to produce the power.
One final way of understanding the light from a flashlight is to consider the foundation of the light and the object, or target of the light.Lumens, the measurement of output, is related to the source of the light.Radiance, the dimension of power, is measured at the thing, or focus on, of the light.
The next time you pick up a flashlight at the hardware store, and you look at the information on the package, don\’t think that lumens equals brightness. If the lens has a close beam, then the radiance will be large. If the lens has a wide beam, the radiance will be moderate.The best way of getting around this problem is to buy a flashlight with a movable lens. These lenses permit you to change the focus of the light. The narrow light will display the largest radiance. The wide beam would be the lowest radiance.