National Physical Laboratory

Luminous intensity, illuminance, luminance or CCT

Photometry Lamps

NPL's first interests in the field of photometry date back to 1902 and we have since established ourselves as world leaders in the area. As such. we are able to offer expertise regarding quantities including luminous intensity and illuminance, luminance and correlated colour temperature of sources and meters.

Our directional photometry facility provides a UKAS accredited calibration service for the measurement of these quantities for tungsten based sources and detectors. Measurements of sources are performed using a high accuracy photometer, which has been specially designed and built at NPL to closely match the visual response of the human eye; described by the V(λ) function.

All photometric measurements are traceable to the UK's primary standard for the measurement of optical radiant power (cryogenic radiometer) through lamps which form part of NPL's luminous intensity scale. NPL also supplies calibrated lamps for luminous intensity, illuminance and colour temperature measurement.

Facility Details

Directional photometric facility and correlated colour temperature facility

  • 8 m optical bench
  • NPL high accuracy photometer
  • High specification colorimeter colour temperature measurements
  • Telephotometer and calibrated white tile for illuminance measurements


  • Luminous Intensity: 1 to 10,000 cd
  • Illuminance: 1 to 50,000 lux
  • Luminance: 1 to 10,000 cdm-2
  • Correlated Colour Temperature: 2000 to 3200 K

Transfer standards

  • Tungsten based lamps; also available calibrated with accredited certification

Other Photometers and Luxmeters

  • Photometer spectral responsivity calibration facility
  • Luxmeter calibration facility


Customer Service tel: +44 20 8943 6151

Last Updated: 25 Mar 2010
Created: 10 Aug 2009


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