$H_{\text{act}}={\displaystyle \int {\displaystyle \int E_{\text{e},\lambda }(t)s_{\text{act}}(\lambda )\text{d}\lambda \text{d}t}}$

where E_e,λ is the spectral irradiance in W·m⁻²·nm⁻¹ and s_act(λ) is the actinic action spectrum normalized to 1 at its maximum

Note 1 to entry: This definition is based on the assumption that an action spectrum is adopted for the actinic effect considered, and that its maximum value is 1.

Note 2 to entry: It is essential to specify which actinic action spectrum is used, as the unit is the same for any action spectrum.

Note 3 to entry: The actinic dose is expressed in joule per square metre (J·m⁻²)

Note 4 to entry: This entry was numbered 845-06-23 in IEC 60050-845:1987.