PreProcessing

As of version 1.1, the RELION GUI implements a semi-automated data preprocessing procedure. This procedures consists of three steps, each of which may be performed independently. The advantage of this procedure is ease-of-use (suitable STAR files and images are created with minimal user intervention) as well as speed (all three steps are MPI-parallelized).

CTF estimation

The relion_preprocess program will launch the CTFFIND3 executable as indicated on the GUI. Apart from the general microscopy settings on the first tab of the GUI, the second tab contains entries for all usual CTFFIND3 parameters. Use wildcards (filenames with * or ?) to select multiple micrographs (in MRC format!) to work on.

In some cases there are parts of the micrograph that are unsuitable for CTF estimation (e.g. labels on film). If that is the case, one may use the Estimate CTF on window size (pix) option to select the size of a squared window, placed at the center of the micrograph, that will be used for CTF-estimation.