Difference between the continuum of synthetic spectral energy distributions (SED) and the estimate obtained from a power law fit to these SEDs (model) using Y, J, and H filters. The magnitude difference between J_model and J_sed is plotted against the magnitude difference between SED and model directly at the wavelength of Hα (cf. Sect. 4.2). The range of SED parameters, for which results are shown, is summarized in Table 1. For the Z = 0.05 panel, a wider axis scale was chosen than in the other two cases. The narrower range used for Z = 0.008 and Z = 0.020 = Z_⊙ is indicated as dotted box in the Z = 0.05 case. The cross in the Z = 0.020 plot represents the SED, which was used for the parameter estimation test described in Sect. 4.3.