Convert between candela (cd), candle, lumen/steradian (lm/sr), and other luminous intensity units with scientific precision.
The SI unit of luminous intensity, defined as the luminous flux emitted per unit solid angle. One candela produces one lumen of luminous flux per steradian. 1 cd = 1 lumen/steradian.
Common uses: Light source specifications, lamp brightness ratings, flashlight intensity, headlight standards, and photometric measurements.
The modern standard candle unit defined as approximately equal to candela. 1 candle ≈ 1 candela. The term "candle power" historically referred to the luminous intensity of specific reference candles.
Historical context: Originally based on the light output of spermaceti candles, standardized for consistent luminous intensity comparisons.
A historical unit of luminous intensity. 1 German candle ≈ 0.95 candela. Used in 19th-century German scientific standards before international standardization.
Historical note: Part of the various national standards before the modern SI system was adopted internationally.
A historical British unit of luminous intensity. 1 UK candle ≈ 0.96 candela. Used in British scientific work during the 19th and early 20th centuries.
Application: Found in older British scientific literature and historical lamp specifications.
A German unit of luminous intensity based on a specific amyl acetate lamp. 1 Hefner candle ≈ 0.9 candela. Used in German-speaking countries during the 19th century.
Historical context: Named after Friedrich von Hefner-Alteneck. Defined the output of a standardized lamp for comparative measurements.
A French unit of luminous intensity based on the Carcel lamp. 1 carcel ≈ 9.6 candela. Used in French scientific standards during the 19th century.
Application: Historical French lighting standards and scientific measurements. The Carcel lamp was a standardized oil lamp used as a reference light source.
A unit based on the light output of a pentane lamp burning under standard conditions. 1 pentane candle ≈ 1 candela. Used as a standard reference in scientific measurements.
Application: Scientific calibration and historical photometric standards. The pentane lamp provided a reproducible light source.
The SI definition of luminous intensity based on luminous flux. 1 lm/sr = 1 candela. Represents the luminous flux per unit solid angle.
Application: Precise photometric calculations, optical system design, and scientific measurements of light sources.