radiometria

Radiometria, or radiometry in English, is the branch of metrology that concerns the measurement of electromagnetic radiation in all wavelengths. It quantifies the power and energy carried by light, independent of human vision, making it distinct from photometry, which weights light by the eye’s response.

Radiometric quantities include radiant flux (phi, in watts), radiant flux density or irradiance (W/m^2) incident on a surface, and radiant exitance (W/m^2) emitted by a source. For a direction, radiometric intensity is measured in W per steradian, and radiance is expressed as W/(sr·m^2). Spectral radiometry uses wavelength-specific forms, such as spectral radiance L_lambda in W/(sr·m^2·nm) or W/(sr·m^2·μm).

Instruments such as radiometers and spectroradiometers measure these quantities. Detectors, calibration sources (e.g., calibrated lamps and blackbodies), and electronics must be traceable to SI units. Calibration and characterization address responsivity, linearity, and spectral response, often following standards from ISO and CIE.

Applications cover remote sensing, astronomy, climate science, solar energy characterization, material testing, and optical engineering. Radiometric data underpin sensor calibration, energy balance studies, and radiometric correction of images, enabling comparisons across instruments and time.

Notes: Radiometry focuses on physical power; photometry focuses on perceived brightness and uses luminous quantities. The atmosphere and instrumental effects require corrections to retrieve true radiometric values.