Luminanssissa

Luminanssissa is the Finnish term used to refer to luminance, the photometric quantity that expresses the perceived brightness of a surface under specified viewing conditions. The phrase is commonly used to describe values or phenomena within the luminance domain of an image, display, or scene.

Luminance differs from brightness as a subjective percept. Luminance is measured in candela per square meter (cd/m^2) and is directional: it describes how bright a surface appears to an observer looking from a particular direction. By contrast, illuminance (lux) measures the amount of light incident on a surface.

In digital imaging, the luminance component is often carried by a Y' channel in color spaces such as Y'CbCr or Y'UV, or as luma in JPEG and MPEG. This channel represents a perceptually weighted combination of the red, green, and blue channels; gamma correction affects the mapping to luminance.

Measurement and standards: Luminance is measured with photometers or spectroradiometers, with geometry and source spectra specified. Typical display luminance ranges: standard dynamic range monitors often reach tens to hundreds of cd/m^2; high dynamic range displays can exceed 1000 cd/m^2.

Applications: Luminanssissa concepts underpin display calibration, HDR imaging, color science, vision research, and quality control in imaging and lighting design. The term helps describe how bright a surface or image should appear to maintain correct contrast and perceptual fidelity in real-world viewing conditions.

See also: luminance, luma, illuminance, color spaces.