Quality of the images obtained with different input FWHM (major and minor axes equal, position angle is zero). The image quality is measured in three ways: (1) the normalized cross-correlation against the true image, or NXCORR; (2) the normalized root-mean-square error against the true image, or NRMSE, shown in the top panel; and (3) reduced χ² goodness-of-fits to the three data products used in the reconstructions (visibility amplitudes, closure amplitudes and phases) shown in the bottom panel. NRMSE is more sensitive to subtle differences in the images than NXCORR due to the higher weight associated with large pixel-by-pixel errors and is minimized in a comparable range of input FWHMs to the reduced data χ². The narrow range of FWHMs encompasses the true mean source FWHM (magenta vertical line).