Candela is Lumen density per solid angle. A sphere emitting 1 Candela uniformly in all directions produces 4π Lumen total power.
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1 Watt equals 683 Lumens of light power at wavelength 555 nm. At other wavelengths 1 Watt is less Lumens as it takes into account the sensitivity of the average human eye.
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Luminous intensity is a measure of the amount of light emitted from a source in a particular direction per unit solid angle. It is a fundamental concept in photometry, which is the science of measuring visible light as perceived by the human eye. The unit of luminous intensity in the International System of Units (SI) is the candela (cd).