Define light

Foot Candles:

•  How bright the light is one foot away from the source.

Lumens:

• Each unit of measurement of light. A lumen is a way of measuring how much light that gets to what you want to light! A LUMEN is equal to one foot-candle falling on one square foot of area.

Radiance:

• Is another way of saying how much energy is released from that light source

Illuminance

• Is the intensity or degree to which something is illuminated and is therefore not the amount of light produced by the lightsource.

LUX

• Is the measurement of actual light available at a given distance. A lux equals one lumen incident per square meter of illuminated surface area. They are measuring the same thing, just using different measurement units.

Candela

• Nowadays we use the term CANDELA instead of candlepower. Candlepower, or CANDELA is a measure of how much light the bulb produces, measured at the bulb, rather than how much falls upon the thing you want to light up. Further confusing the matter is beam focus. That's how much candlepower can be focused using a reflector/lens assembly. Obviously, if you project all your light bulbs intensity at a given spot, or towards something, it will be more intense, and the illuminance will be higher.

• For you figuring out LED equivalents, first you must know how many lumens your LED's each produce. Then divide that value by 12.57 and you have candlepower of the LED. You don't have foot-candles, remember foot-candles are illuminance. And we are measuring radiance.

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