Synthetic low-resolution spectra (R = 360) for three dynamic model atmospheres as denoted in the legend. Plotted are spectra based on the corresponding hydrostatic initial model as well as two representative phases of the dynamic calculation (φ_bol ≈ 0.0 and 0.5). The insert in the middle panel shows the absorption data for amorphous carbon dust from Rouleau & Martin (1991) as applied in the modelling. The wavelength ranges of the used broad-band filters (≈FWHM of the responses given in Bessell (1990) and Bessell & Brett 1988) are marked for orientation purposes in the lower panel.