Luminous Intensity Converter

About This Tool

This Luminous Intensity Converter is a tool for photometry and lighting science. It converts units of luminous intensity, which is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle. The base unit is the candela (cd), one of the seven SI base units.

Luminous intensity describes the directional strength of a light source. It is fundamental to defining other photometric quantities like luminance (brightness) and illuminance (light falling on a surface). This tool includes the modern candela as well as several historical 'candlepower' standards.

Tips & Features

• The Candela: The modern candela is the fundamental unit. It is defined based on the luminous efficacy of a specific frequency of light, tying it to radiometric units. One candela is approximately the luminous intensity of a common wax candle.
• Luminous Intensity vs. Luminous Flux: Luminous intensity is directional (power per solid angle, measured in candelas). Luminous flux is the total light emitted in all directions (measured in lumens). A spotlight might have a very high luminous intensity (many candelas) in its beam but a modest total luminous flux (lumens).
• Historical Units: Before the modern candela was standardized, various countries had their own 'candlepower' standards, often based on the light produced by a physical lamp of a specific design.