Correlations between the predicted magnification of an image as a function of image position for a source at redshift z = 1 and the different input parameters which are optimized in the model for A2204 (compare Table 2 and Fig. 3) in a field of view  ± 100 arcsec around the cluster center. Correlations are given as the absolute values of the correlation coefficients. The last panel shows an ACS image of the cluster overlaid with the critical lines for z = 1.