Comparison of the fluxes from SDSS DR5 and HST WFPC2 observations. These panels show the ratio between the HST and the SDSS fluxes as a function of the HST flux. The average difference and standard deviation are listed in the bottom right of each panel. In the left panel, we show the ﹩( \mathrm{F}\,606\mathrm{W}\,-V_{\mathrm{eff}\,}) ﹩ residual for the objects which were only observed in the V‐band and had SDSS data. Since the average difference is only −﹩0.08\pm 0.79﹩ mag, the conversion from ﹩g^{\prime }﹩ and ﹩r^{\prime }﹩ to ﹩V_{\mathrm{eff}\,}﹩, and hence the correlation shown in Fig. 5 is relatively robust. The right panel shows that the once the V‐band measurements are converted to the ﹩i^{\prime }﹩ band, there is relatively little additional error introduced by assuming that ﹩i^{\prime }\approx I﹩ for these radio galaxies.