Lux Meters (Light Meters)

Lux meters or light meters measure illumination in terms of luxes (lx) or foot candles (fc). A lux is equal to the total intensity of light that falls on a one square meter surface that is one foot away from the point source of light. A foot candle is equal to the total intensity of light that falls on a one square foot surface that is one foot away from the point source of light. Most lux meters or light meters consist of a body, photo cell or light sensor, and display. The light that falls onto the photo cell or sensor contains energy that is converted to electric current. In turn, the amount of current depends on the amount of light that strikes the photo cell or light sensor. Lux meters read the electrical current, calculate the appropriate value, and output the results to an analog, digital, or video display. Since light usually contains different colors at different wavelengths, the reading represents the combined effects of all the wavelengths. Typically, standard colors or color temperatures are expressed in degrees Kelvin (K). The standard color temperature for the calibration of most lux meters is 2856° K, an amount that is more yellow than pure white.

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