Scientists measure the brightness of a light source in units of candles or, when using the metric system, in candelas. The amount of illumination -- or illuminance -- a surface receives depends on the distance from the light source and the intensity of the light source. Illuminance is measured in either foot-candles or the metric system units of lux. You can readily change foot-candles to lux by using a simple numerical conversion factor.
The unit name foot-candle can be abbreviated as "fc" or "ftc."
Enter the numerical value of illuminance, in units of foot-candles, into the calculator. For example, if your illuminance value is 22 foot-candles, you would enter 22.
Multiply the value which you just entered by 10.76. This is the conversion factor between foot-candles and lux. In the above example, you would calculate 22 x 10.76 = 237.
Report the result of the previous calculation as the illuminance in units of lux. You have now converted the original value of illuminance in units of foot-candles to units of lux. The example would therefore be reported as 237 lux.
- University of North Carolina at Chapel Hill; How Many? A Dictionary of Units of Measurement; C; R. Rowlett
- North Dakota State University: PLSC 210-Horticulture Science: Chapter 9: Lights and Lighting
- University of North Carolina at Chapel Hill; How Many? A Dictionary of Units of Measurement; F; R. Rowlett
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