Example of the photometric calibration fit obtained for all stars in common with previous WINGS photometry. In this example we used data from MKW3s observations. The left panels show the difference between calibrated WINGS INT photometry and instrumental OmegaCAM magnitudes as a function of the B−V colour. The upper and lower panels show the results for B- and V-band photometry, respectively. The linear fit shown as a blue line was obtained by clipping out outliers (black dots). The distribution of the residuals is well described by a Gaussian function, shown in the right panels.