Foot-candle

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foot-candle

A unit of illuminance or illumination equal to one lumen per square foot.

This is the illuminance provided by a light source of luminous intensity one candela (formerly candle) at a distance of 1 ft, hence the name. Full sunlight with zenith sun produces an illuminance of about 10 000 foot-candles on a horizontal surface. Full moonlight provides an illuminance of about 0.02 foot-candles. Adequate illumination for reading is taken to be about 10 foot-candles; that for machine shop work is about 40 foot-candles.
Compare lux.

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