= Photon count spectral luminosity
{title2=$L_\varepsilon^N=dN/(dt\,d\varepsilon)=L_\nu/(h\varepsilon)$}
For <photon> <energy> $\varepsilon=h\nu$, equating radiated <energy> in corresponding spectral intervals gives $L_\nu\,d\nu=\varepsilon L_\varepsilon^N\,d\varepsilon$. Thus $L_\varepsilon^N=L_\nu/(h\varepsilon)$. A quoted rate per joule must be multiplied by the number of joules per <electronvolt> or per $\mathrm{keV}$ to express it in that spectral unit. For homogeneous <optically thin> emission, $L_\nu=4\pi Vj_\nu$ if $j_\nu$ is defined per <solid angle>.
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