international candle

An obsolete unit of luminous intensity first defined in 1909 at a meeting of representatives of the Laboratoire Central de l’Electricité (France), the National Physical Laboratory (Britain), the Bureau of Standards (United States) and the Physicalische Technische Reichanstalt (Germany). The Germans decided to let 1 international candle equal ⁹⁄₁₀ths of the output of a Hefner lamp; the other nations, however, established a standard using an electric lamp with a carbon filament.

In 1921, the Commision Internationale de l’Eclairage (International Commission for Illumination, commonly referred to as the CIE) redefined the international candle in terms of a carbon filament incandescent lamp.

In 1937, the international candle was redefined by saying the luminous intensity of a blackbody at the freezing point of liquid platinum would be 58.9 international candles per square centimeter. In 1946, the CIPM replaced the international candle with the new candle.

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