(EdMark Corporation)(Version 1.0a)(1998).iso/Worldbook/graphics/1px.gif){kind=spacer}
(EdMark Corporation)(Version 1.0a)(1998).iso/Worldbook/graphics/logo.gif){kind=logo}
Foot-Candle
Foot-candle is a unit of measurement of illumination, the amount of light that falls on an object. The foot-candle is part of the customary system of measurement.Two factors determine the amount of light an object receives: (1) the luminous intensity (the amount of light a light source produces) and (2) the distance between the light source and the object. As the luminous intensity increases, illumination also increases. As the distance increases, illumination decreases by the square of the distance.
To calculate in foot-candles the illumination (E) on a surface perpendicular to a light ray, scientists use the formula E = I/D-squared. I is the luminous intensity in candelas (see Candela). D is the distance in feet between the light source and the object.
In the metric system, illumination is measured in a unit called the lux. Distance is measured in meters. One foot-candle equals 10.76 lux.
Contributor: Ronald N. Helms, Ph.D., Chairperson of Architectural Engineering, North Carolina Agricultural and Technical State Univ.; Lighting Consultant; Expert Witness.
Master Index
World Book and the globe device are trademarks of World Book, Inc.