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Lighting Termiology

Quick Reference
Watt: a measure of the total power output of a light source
Lumen: a measure of the total visible light output of a light source
Candlepower: an obsolete term that has been replaced by “candela”
Candela: a measure of the intensity of a light source in a particular direction
▪ Foot-candles and lux: the amount of visible light falling on a surface

Watts & Lumens
It is a common misconception that higher wattage equals higher light output—in part due to the fact that incandescent light output generally increases with wattage numbers.

With LED technology, this is not the case. LEDs can emit the same, if not more light than a bulb, while consuming less power.

Watts are a measure of power consumption, while lumens are a measurement of visible light output.

When you want to know how bright a light will be, you need to identify the lumen output value, not the wattage—especially when comparing LED and bulb-based lights.

Foot-Candles & Lux

Both foot-candles and lux measure the same thing—the amount of visible light that falls on a surface. The difference is that the foot-candle uses the Imperial standard measuring system (feet, pounds, etc.), while the lux uses the metric system (meters, grams, etc.). A single foot-candle is equivalent to the amount of light that falls on a surface that is one foot away from a single candle, and a lux is the amount of light that falls on a surface one meter away from a candle. For conversion, one foot-candle is approximately equal to 10.764 lux.