\begin{table}%t1 \caption{\label{tab:ratio_errors}The flux ratio (Ba/Bb) of \epsba, Bb~in the observed FORS2 and ISAAC~filters and the effective wavelength and half-power width of those filters.} \small%\centerline { \begin{tabular}{clll} \hline \hline\noalign{\smallskip} Observed passband & Ratio (Ba/Bb) & $\lambda_{\rm{eff}}~(\mu$m) & $\Delta\lambda~(\mu$m) \\ \hline $V$ & 9.82 $\pm$ 0.66 & 0.554 & 0.112 \\ $R$ & 4.81 $\pm$ 0.07 & 0.655 & 0.165 \\ $I$ & 5.04 $\pm$ 0.05 & 0.768 & 0.138 \\ $z$ & 3.85 $\pm$ 0.03 & 0.910 & 0.131 \\ $J$ & 2.28 $\pm$ 0.02 & 1.25 & 0.29 \\ $H$ & 5.27 $\pm$ 0.06 & 1.65 & 0.30 \\ $K_{\rm{S}}$ & 7.12 $\pm$ 0.02 & 2.16 & 0.27 \\ $L$ & 4.50 $\pm$ 0.16 & 3.78 & 0.58 \\ $M_{\rm{NB}}$ & 1.35 $\pm$ 0.15 & 4.66 & 0.10 \\ \hline \end{tabular}} \medskip See Appendix~\ref{sec:phot_calib} for a description of photometric calibration and transformation to standard systems. All except the $V$-band ratio were measured using PSF-fitting (see~Sect.~\ref{sec:opt_phot}). \end{table}