Understanding the difference between lumens and candlepower is crucial when choosing a flashlight or any light source. While both terms relate to light output, they measure different aspects. This article will delve into the specifics of each measurement and clarify how they relate to one another.
Candlepower measures the brightest part of a beam, essentially its intensity. Imagine a laser pointer: it has high candlepower because its light is concentrated into a tiny, intense spot. Lumens, on the other hand, measure the total amount of light emitted by a source, regardless of its focus. A household light bulb, for instance, might have lower candlepower than a laser but significantly higher lumens because it distributes light over a wider area.
All light measurements originate from the candela, the fundamental unit of luminous intensity, often referred to as candlepower. It’s akin to the older unit, the candle, which was based on the light produced by a candle of specific dimensions.
Flashlight manufacturers typically use two methods to rate light output:
Total Luminous Output: This measures the entire light emitted, irrespective of beam focus. It primarily depends on the lamp itself and is often expressed in lumens or candela. To convert candela to lumens, multiply by 12.57 (π x 4). For example, a 20-watt lamp emitting 450 lumens has a mean spherical candela of approximately 35.8. Mean spherical candela represents the average light intensity in all directions.
Peak Beam Intensity (Candlepower): This quantifies the brightest spot in a focused beam, influenced by both the lamp’s output and the reflector’s efficiency. A flashlight with 20,000 candlepower produces the same light intensity within its hotspot as a bare 20,000 candela lamp at the same distance. High-powered rechargeable flashlights often have candlepower values in the tens of thousands.
It’s important to note that you cannot directly convert between peak beam candlepower and lumens because total output doesn’t consider the reflector’s focusing ability.
Furthermore, all light ratings rely on human eye perception and are therefore subjective. The color temperature, measured in Kelvin (K), also affects perceived brightness. A whiter light (higher color temperature, around 3200K) appears brighter to the eye than a yellower light of the same intensity.
The American National Standards Institute (ANSI), in collaboration with flashlight manufacturers, has established standards to measure and communicate flashlight performance, including brightness (lumens), runtime, beam distance, peak beam intensity (candlepower), water resistance, and impact resistance. Brands like Streamlight, Pelican, and Fenix now utilize these ANSI standards, facilitating easier comparisons between products.
In conclusion, lumens measure total light output, while candlepower measures the intensity of the brightest point in a beam. Understanding both metrics is essential for selecting the right light source for your needs. Consider lumens for overall brightness and candlepower for focused light intensity. Always refer to ANSI standards when comparing flashlights from different manufacturers for a more accurate assessment.
