density of incident photon flux with respect to area at a point on a real or imaginary surface
Note 1 to entry: The corresponding radiometric quantity is "irradiance". The corresponding photometric quantity is "illuminance".
Note 2 to entry: The photon irradiance is expressed in second to the power minus one per square metre (s−1·m−2).
Note 3 to entry: This entry was numbered 845-01-39 in IEC 60050-845:1987.
Note 4 to entry: This entry was numbered 17-929 in CIE S 017:2011.