Valonvoimakkuuden

Valonvoimakkuuden, a Finnish term, translates to luminance in English. It is a photometric measure of the perceived brightness of a surface, essentially how much luminous power is perceived by the human eye to be emitted, reflected, or transmitted from a particular area in a particular direction. Luminance is a key factor in visual perception and is crucial for understanding how we see objects and their surroundings.

The unit of luminance in the International System of Units (SI) is candela per square meter (cd/m²). One candela per square meter represents the luminance of a perfectly diffusing surface that reflects or transmits one lumen of light per square meter. Other units, such as the foot-lambert (fl), are also used, particularly in older or specific industries.

Luminance is not simply about the amount of light emitted by a source, but rather how bright that source appears to an observer. It takes into account the sensitivity of the human eye, which varies with wavelength. For instance, a light source emitting green light may appear brighter than a source of the same intensity emitting red light, even though their radiometric power is the same. This subjective perception is what luminance quantifies.

Applications of understanding luminance are widespread. It is essential in display technology, such as for televisions, monitors, and mobile phones, to ensure images are visible and comfortable to view under various lighting conditions. In photography and cinematography, controlling luminance is fundamental to achieving desired exposure and image quality. Furthermore, luminance plays a role in lighting design for interiors and exteriors, impacting visual comfort and task performance.