${\displaystyle H_{\text{v}}=\frac{\text{d}{Q}_{\text{v}}}{\text{d}A}}$

where Q_v is luminous energy and A is the area on which the luminous energy is incident

Note 1 to entry: The term "light exposure" is no longer used.

Note 2 to entry: Luminous exposure can be derived from the spectral radiant exposure distribution by

$H_{\text{v}} = K_{\text{m}}{\displaystyle \underset{0}{\overset{\infty }{\int }}{H}_{\text{e}\text{,}\lambda }}(\lambda )V(\lambda )\text{d}\lambda$

where K_m is maximum luminous efficacy, H_e,λ(λ) is the spectral radiant exposure at wavelength λ and V(λ) is spectral luminous efficiency. Integral limits can be confined depending on the spectral responsivity of the detectors used as a sensor.

Note 3 to entry: The corresponding radiometric quantity is "radiant exposure". The corresponding quantity for photons is "photon exposure"

Note 4 to entry: The luminous exposure is expressed in lux second (lx·s = lm·s·m⁻²).

Note 5 to entry: This entry was numbered 845-01-43 in IEC 60050-845:1987.