valaistusmäärä

Valaistusmäärä, commonly referred to in lighting practice as illuminance, describes the amount of light incident on a surface. It is a measure of how brightly a space appears to the human eye and is a central parameter in lighting design and evaluation. In practical terms, it indicates whether a surface receives enough light to perform tasks comfortably and safely.

Illuminance is quantified in lux (lx), where 1 lux equals 1 lumen per square meter. It is influenced by the luminous flux from light sources, the distance between the source and the surface, the angle of incidence, and the reflectivity of the surface. For point sources, illuminance roughly follows inverse-square behavior with distance and depends on the source direction relative to the surface. In real environments, reflections and geometry must be considered, making accurate assessment a job for light meters and simulation tools.

Standards and guidance: Illuminance levels are specified for different tasks and environments in international and national standards. Common references include office work, education, healthcare, and outdoor locales, each with recommended ranges of lux to ensure adequate visibility, comfort, and safety. Daylight can contribute significantly to overall illuminance and is often accounted for in lighting design through daylight integration and controls.

Related concepts: Valaistusmäärä complements related quantities such as luminous flux (valovirta) and luminance, and it must be considered alongside factors like glare, color rendering, uniformity, and energy efficiency. In practice, measuring and achieving appropriate valaistusmäärä is essential for functional interiors, occupational health, and compliant building design.