In spectrometers, I also usually saw the radiance (W/m2/nm) divided by E3 (photon energy^3) to get the emission rate in photons per unit spectral energy and per area. I'm getting s^3 nm^-1 m^-4 kg^-2 or s nm^-1 J^-1 m^-3 kg^-1and these units makes no sense for me. How do these units become equivalent to photons per unit spectral energy and per area? Thank you!