Valomittarit

Valomittarit are instruments that measure the intensity of light. In Finnish, valomittari means a light meter, and valomittarit refers to the plural. They are used to quantify exposure in photography and cinematography, and to assess daylighting, horticultural lighting, and occupational safety.

There are several types: handheld light meters, built-in meters in cameras, and specialized meters for studio flash. They are typically divided into incident meters, which measure light falling on a subject using a diffuser, and reflected meters, which measure light reflected from a scene through a sensor. Readings are usually given in lux (or, less commonly, foot-candles); some meters also display luminance.

How they work: a sensor, usually a silicon photodiode or phototransistor, converts light to an electrical signal. The device computes an exposure value based on the measurement, taking into account the film or sensor sensitivity (ISO) and the chosen aperture or shutter speed. Incident meters aim to reflect the actual lighting on a subject, while reflected meters estimate the exposure by the scene’s average reflectivity. Flash meters include separate modes that measure brief light bursts.

Applications: in photography and cinema, valomittarit guide exposure for correct brightness and contrast. In architecture and interior design, they help assess daylight levels and lighting design. In horticulture, they monitor light for crop growth. In workplace safety, they ensure adequate illumination.

Calibration and standards: modern meters are calibrated to national or international standards and are traceable to standard light sources. They often reference the CIE luminous efficiency function V(λ) and report readings in lux or foot-candles. Over time, brands such as Sekonic, Minolta, and Gossen popularized handheld meters.