EMAN

Refine 3d Model

Determine CTF parameters

Once the particles are boxed we may use ctfit to determine the ctf parameters. Knowing the ctf parameters is necessary in order to classify the particles into classes  and to align the particles within these classes. The ctf parameters include the microscope parameters (spherical aberration coefficient,  the defocus, as well as temperature factor) as well as the parameters that describe the effects of the noise (for which there are 5). This information is written into the headers for the particle files and are read by the classification and alignment programs.

At this point also, the phases are flipped (see ctfit). So besides the new header information, the particles themselves are modified.


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Last Modified: Feb  7 14:43:58 CST 1999