Comparison of the dilute blackbody models from {V,I} (red) and {B,V,I} synthetic photometry (green) to the original TARDIS spectrum (blue). The spectrum is our SN1999em model for the 9th of November (see Fig. 2). The parameters of the blackbody fits are T_VI = 9500 K, T_BVI = 10 200 K and ξ_VI = 0.49, ξ_BVI = 0.45. We have overplotted the transmission curves for the B, V and I filters from Bessell (1990). The Monte Carlo spectrum has been smoothed using a Savitzky–Golay filter (Savitzky & Golay 1964).