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) Intensity (physics), the name for irradiance used in other branches of physics (W/m2) Radiance, commonly called "intensity" in astronomy and astrophysics (W·sr−1·m−2)
See also 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