Several measures of light are commonly known as intensity:

  • Radiant intensity, a radiometric quantity measured in watts per steradian (W/sr)
  • Luminous intensity, a photometric quantity measured in lumens per steradian (lm/sr), or candela (cd)
  • Irradiance, a radiometric quantity, measured in watts per square meter (W/m2)
  • Radiance, commonly called "intensity" in astronomy and astrophysics (W·sr−1·m−2)

See also

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  • Brightness, the subjective perception elicited by the luminance of a source
  • Luminance, the photometric equivalent of radiance (lm·sr−1·m−2)
  • Photometry (optics), measurement of light, in terms of its perceived brightness to the human eye
  • Radiometry, measurement of light, in absolute power units
  • Luminosity