density of incident photon number with respect to area at a point on a real or imaginary surface
Note 1 to entry: The corresponding radiometric quantity is "radiant exposure". The corresponding photometric quantity is "luminous exposure".
Note 2 to entry: The photon exposure is expressed in metre to the power minus two (m−2).
Note 3 to entry: This entry was numbered 845-01-44 in IEC 60050-845:1987.
Note 4 to entry: This entry was numbered 17-924 in CIE S 017:2011.