Ljusstyrkavärde

Ljusstyrkavärde, often translated as luminous intensity value, is a term used to quantify the perceived brightness of a light source. It specifically refers to the amount of light emitted by a source in a particular direction. The standard unit for luminous intensity is the candela (cd).

A candela is defined as the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 × 10^12 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian. This definition is based on fundamental physical constants.

Luminous intensity is crucial in various applications, including lighting design, photometry, and the specification of light-emitting devices. For example, when choosing a light bulb, its luminous intensity in different directions contributes to how well it illuminates a specific area. Spectrophotometers and other optical instruments often measure luminous intensity to characterize light sources.

It is important to distinguish luminous intensity from other photometric quantities like luminous flux (measured in lumens), which represents the total amount of visible light emitted by a source in all directions, and illuminance (measured in lux), which describes the amount of light falling on a surface. Luminous intensity is directional, making it a more precise measure for understanding how a light source behaves in a specific orientation.