Actually when the Fourier transform of an EM is indexed and diffraction intensities and phases are measured, the corresponding EM is averaged according to the lattice periodicity. Here the averaging is done further according to the space group symmetry by forcing both the amplitude and phase of structure factors to obey the symmetry relationships*. The calculation is first carried out in reciprocal space. Make the sub window containing the reciprocal image (on the left) the current window. Click the 'Sym. average' button  . The averaged reciprocal image (on the right) is obtained by following the direction of a few dialog boxes.

* For details the user is referred to Xiaodong Zuo, Chem. Commun., Stockholm Univ. 1995, No. 5, pp. 38-42.

        Fourier transforming the averaged reciprocal image (on the left), we get the average image in real space (middle). The latter can be zoomed by clicking the 'Zoom' button  . Be sure to adjust also the 'Width' and 'Height' in the dialog box to fit your need. The green lines on the enlarged image (on the right) are unit cell borders which can be shown or hid using the corresponding function in the 'Image' pull-down menu.