• Particle box-size - Impacts quality and speed of reconstructions!

• Supported image file formats and usage
• How EMAN2 stores data in HDF5 files
• Header information (key/value pairs) associated with a specific image
• Information stored in JSON files in the info/ folder and elsewhere
• Setting local and global application preferences
• Other misc. files such as .box and .lst

• Symmetry in EMAN2, and generating projections in an asymmetric unit
• Angular sampling, number of projection and resolution
• 3D and 2D Transformations (rotation, translation, etc.)
• CTF model used in EMAN2

Many aspects of EMAN2 are modular, meaning new functions can be easily added for a variety of tasks. These categories are used in the GUI and from the command-line, and are not just useful for programmers. For example, the '–process' option in e2proc2d.py and e2proc3d.py uses 'processors' as defined below.

Note: These pages are often out of date. For up to date details please run

e2help.py <object type> -v 2

• Overview of how to use modular functions
• Processors - Filters, masks and other basic image processing operations
• Comparators (cmp) - Similarity metrics (cmp) for comparing two images/volumes
• Aligners - Algorithms for aligning one image/volume to another
• Averagers - Methods for averaging many images/volumes together
• Projectors - Generate 2-D projections of 3-D volumes (or 1-D projections of 2-D images)
• Reconstructors - Generate 3-D volumetric reconstructions from sets of 2-D images and orientation paramters
• Analyzers - Perform various analyses on sets of images/volumes
• Symmetries - Permissible symmetries to use in EMAN2
• Orientation Generators (orientgen) - Methods for generating sets of orientations filling an asymmetric unit