Photometry - definition
Photometry - definition
Photometry is a branch of optics concerned with the measurement of light in a way that accounts for the sensitivity of the human eye. Unlike radiometry, which describes the physical properties of electromagnetic radiation, photometry focuses on quantities related to visual perception, such as illuminance, luminance, luminous flux, and luminous intensity. Measurements are based on the spectral luminous efficiency curve, which reflects the eye’s relative sensitivity to different wavelengths within the visible spectrum.
The primary SI unit in photometry is the lumen, which represents the amount of light emitted by a source. Other units, such as lux and candela (cd), describe the spatial distribution of light and its interaction with surfaces. Photometry plays a crucial role in the design of lighting systems, the evaluation of light source quality, and the analysis of visibility conditions in public spaces, architecture, and industry.
Photometry applications include both laboratory measurements and practical lighting assessments in real-world environments. Modern measurement systems use precision photometers equipped with filters that correct the spectral response of detectors to closely match the characteristics of human vision. This enables the quantitative evaluation of visual comfort, lighting energy efficiency, and compliance with photometric standards. Photometry is also important in display technology, visual engineering, and the study of optical materials.
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