Left: comparison of input stellar spectra for photoionization models showing a realistic SED (blue line; Pop III, Salpeter IMF 1−100 M_⊙ at zero age) and the corresponding black body spectrum (red line) with the same average photon energy ( eV) in the Lyman continuum. The SED model is normalized at 1240 Å and the rest rescaled to match the same ionizing flux Q(H). Right: input stellar spectra (dash-dotted, same colours as left panel) and predicted nebular and total continua from our CLOUDY models for log (n(H)) = 1 cm^-3 and log (U) = −1 (solid lines, using the same colours as in left panel; cf. also inset for symbols). The green solid line shows the total (stellar + nebular) SED from our evolutionary synthesis model assuming constant nebular density and temperature and case B. Notice the difference between case B and the CLOUDY result due to enhanced 2γ emission.