Comoving photon distribution in the five different zones as obtained by Komrad dynamical. The line coding is shown by the legend in the top-left panel, where RS and FS stand for reverse shock and forward shock, respectively. The four different panels show the distributions at different optical depths, corresponding to the optical depths in Figure 3. The observed photon distribution consists of a superposition of comoving spectra, leading to a smoothening and broadening effect on the observed spectrum. The simulation parameters are given in Table 1.