Light Output Measurements: Difference between revisions
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==Candela== | ==Candela== | ||
Candela is another SI unit, but is calculated in such a way so that it does not vary with distance. This is done by simply taking the value in lux and multiplying it by the square of the distance to the emitter (in meters). Taken at a distance of 1 meter, a reading of 1 lux indicates 1 candela. At 10 meters, a measurement of 1 lux would indicated 1 x 10² = 100 candela. Like a lux reading, it will vary depending on whether the reading is taken in the hotspot or spill of the light, so the measurement is usually taken at the brightest spot. Therefore the candela value is really a measurement of how far a flashlight will throw a beam. One candela represents the light intensity of a single candle and is roughly equal to the now obsolete non-SI unit "candlepower." See [http://en.wikipedia.org/wiki/Candela Wikipedia article] for more information on candela. | Candela (cd) is another SI unit, but is calculated in such a way so that it does not vary with distance. This is done by simply taking the value in lux and multiplying it by the square of the distance to the emitter (in meters). Taken at a distance of 1 meter, a reading of 1 lux indicates 1 candela. At 10 meters, a measurement of 1 lux would indicated 1 x 10² = 100 candela. Like a lux reading, it will vary depending on whether the reading is taken in the hotspot or spill of the light, so the measurement is usually taken at the brightest spot. Therefore the candela value is really a measurement of how far a flashlight will throw a beam. One candela represents the light intensity of a single candle and is roughly equal to the now obsolete non-SI unit "candlepower." See [http://en.wikipedia.org/wiki/Candela Wikipedia article] for more information on candela. | ||
==Throw== | ==Throw== | ||
An actual distance for throw can be directly calculated from the candela value and will be given in meters. The FL-1 standard does just this by providing a light intensity reading in candela and converting this to throw in meters by calculated the distance at which the light will generate 0.25 lux. Throw is just the square root of the light intensity in candela divided by 0.25 lux which gives meters. | An actual distance for throw can be directly calculated from the candela value and will be given in meters. The FL-1 standard does just this by providing a light intensity reading in candela and converting this to throw in meters by calculated the distance at which the light will generate 0.25 lux. Throw is just the square root of the light intensity in candela divided by 0.25 lux which gives meters. | ||