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Joined 2026-09-21 Message
Incoming links: Realization of the candela
Photometer 2026-10-14
A photometer measures a visually weighted radiation quantity. A filtered photodiode approximates the photopic luminous efficiency function with its spectral responsivity; calibration establishes how its electric current maps to illuminance or collected luminous flux. NIST's detector-based realization traces the spectral responsivity to a cryogenic radiometer and the aperture area to length measurements. [ref]
Photometric matching filter 2026-10-14
A photometric matching filter shapes a photodiode's combined spectral responsivity toward the photopic luminous efficiency function. Matching is imperfect, so photometric calibration must retain spectral information. [ref]