Photometry and Radiometry
Radiometry is the metrology branch devoted to electromagnetic radiation measurements, included visible light. In particular, photometry measures the visible light taking into account sensibility of optical human system. While radiometry performs light measurements over the complete electromagnetic spectrum, photometry is limited to visible range, between 380 nm and 830 nm, where human eye is sensitive.
All radiometric quantities have a corresponding photometric quantity where power or energy are conveniently weighted by visible perception typical of human observer. The photometric quantity Luminous intensity is one of the seven base units of the International System (SI); the corresponding measurement unit is the candela (cd).
Photometry is essential to evaluate light sources and generally lighting devices, luminous signals, display and every application where the light has to be seen by human observers.
Radiometry, on the other hand, is important in all those applications where human being is not involved, but a measurement in terms of energy and/or power is necessary, as for example the characterisation of optical fibre devices, photovoltaic installations, photolithography for nano-micro-fabrication, optical sensors for environment monitoring, power lasers used in metal cutting and welding, single photon methods for quantum technologies.
INRIM participates to International Technical Reference Committees:
- CCPR, Consultative Comittee for Photometry and Radiometry
- EURAMET TC-PR, Technical Committee for Photometry and Radiometry