== Comparators (cmp) ==

To get a current list of Comaparators, run '''''e2help.py cmp''''' or for more detailed information '''''e2help.py cmp -v 2'''''.

The most commonly used comparators and options are:

 * ccc - simple cross correlation coefficient (dot product). Causes orientation bias for some particles, but generally good for initial coarse alignments.
 * frc:snrweight=1:zeromask=1 - Integrated Fourier ring correlation coefficient, in this case with SSNR weighting and noise masking. This is the standard for the highest resolution reconstructions. If used without snrweight=1, it is important to set a good maxres= value instead.
 * phase:snrweight=1:zeromask=1 - Similar to frc, but uses mean phase error instead.