Prepare input files

Experimental images

RELION reads the following image file formats:

• MRC individual images (with extension .mrc)
• MRC stacks (with extension .mrcs) (recommended)
• SPIDER individual images (with extension .spi)
• SPIDER stacks (with extension .spi)

Preparation of the images is explained on the Preprocess images page.

If no CTF-correction is to be performed inside RELION, then a stack of images may be used directly as input (command line option --i). In that case, it is recommended that the images are CTF-phase flipped before refinement. If CTF-correction is to be performed inside RELION (recommended for cryo-data), then besides the images themselves, also metadata regarding the CTFs needs to be provided. In that case, the input to RELION is done using a STAR file (see below).