Dilution factors as a function of colour temperature as inferred from blackbody fits (dots) compared to the dilution factors for Type IIP SNe determined by Dessart & Hillier (2005) (solid lines) for the B and V (upper left panel), the B, V and I (upper right panel), the V and I (lower left panel) and the J, H and K (lower right panel) bands. In all panels we also show the upper and lower error bars for the systematic error arising from the extinction and distance.