To understand the advertising about lights which claim “80 lumens” or “1,000,000 candlepower,” you need to understand what those things are. To put it simply, lumens are a measurement of how much light a device produces, and candlepower is a measurement of concentration of the beam a device produces. These are not the same thing.
The important point here is: Just because a light produces more candlepower, that doesn’t mean it produces more light. More candlepower isn’t always better, either – would you use a laser-pointer (which has high candlepower for its brightness) to light up a room? In other words, some flashlights produce a very thin, strong beam which travels for great distances, something that is great for spotting objects a good distance away but very poorly suited to lighting up a general area or searching for something up close. In general, lights that have wide beams good for close-range work are poor for long-range work and vice-versa. A light that has an “in the middle” beam is usually the best choice for most people. Thankfully, fewer and fewer flashlight manufacturers are bothering to rate their products with candlepower, and lumens are being listed more often as time continues. A good rule of thumb is, “Lumens are brightness, candlepower is beam shape. Buy the number of lumens you need with the beam shape for the job
Here are the definitions of some units:
One candlepower is the radiating power of a light with the intensity of one candle. This unit is considered obsolete as it was replaced by the candela in 1948, though it is still in common use. 1 candlepower is equal to about 0.981 candela. *
The standard unit for measuring the intensity of light. The candela is defined to be the luminous intensity of a light source producing single-frequency light at a frequency of 540 terahertz (THz) with a power of 1/683 watt per steradian, or 18.3988 milliwatts over a complete sphere centered at the light source. *
The standard unit for measuring the flux of a light being produced by a light source. One lumen represents the total flux of light emitted, equal to the intensity in candelas multiplied by the solid angle in steradians (1/(4·pi) of a sphere) into which the light is emitted. *
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