Ljusexponering

Ljusexponering is a term used in Scandinavian languages to describe the amount and duration of light exposure received by a person or object. Broadly, it encompasses natural daylight as well as artificial lighting. It can be quantified in photometric units such as lux, which measures illuminance on a surface, and in cumulative terms as lux-hours. In radiometric terms, irradiance is expressed in watts per square meter. In photography and film, ljusexponering also refers to the total light reaching a sensor or film, determined by the exposure triangle of aperture, shutter speed, and sensitivity (ISO).

For humans, light exposure is a key regulator of circadian rhythms. Light detected by the retina, especially by intrinsically photosensitive retinal ganglion cells, influences melatonin production and alertness. Daylight exposure during daytime supports wakefulness and mood, while exposure in the evening or at night, particularly to blue-enriched light from screens, can delay sleep and disrupt circadian timing. Adequate outdoor exposure in children has been associated with various health benefits, including better visual development and sleep patterns; excessive bright light without protection carries risks such as skin damage and retinal hazard, underscoring the importance of sun safety.

Applications and design considerations include lighting design, architecture, and urban planning, where daylight exposure is leveraged to improve wellbeing and reduce energy use. In photography and videography, proper ljusexponering yields correctly exposed images, with practitioners adjusting aperture, shutter speed, and ISO to achieve desired brightness and contrast. Safety guidance emphasizes avoiding direct staring at very bright sources and following protective measures for skin and eyes when exposed to intense or prolonged light.