T_?,? respectively, are defined as
:
:where
*L_e,?,?^t is the spectral radiance in frequency transmitted by that surface;
*L_e,?,?ⁱ is the spectral radiance received by that surface;
*L_e,?,?^t is the spectral radiance in wavelength transmitted by that surface;
*L_e,?,?ⁱ is the spectral radiance in wavelength received by that surface.

Luminous transmittance