Upper panels: V − I versus B − V relations derived from the SPoT models (left panel Raimondo et al. 2005, models are shown with crosses), and from the integrated colours of Virgo cluster galaxies (right panel). The linear fit to models is shown with dashed line. Lower panels: difference between the distance moduli obtained using the SBF calibration from the V − I colour and from the . Each panel shows the case of V − I derived from the relations shown in the upper panels, as labelled.