Hi David,
Some of the delocalised signal is put back into the particle box by
premultiplication with the CTF, prior to boxing out. One then needs to
tell relion_refine that the data is ctf_premultiplied. This is then no
longer done inside the Wiener filter that forms the core of the
maximisation step inside the refinement. The option is somewhat
developmental. We've never observed huge improvements when compared to the
standard way of running relion. Therefore, for now it's not accessible
from the GUI.
HTH,
Sjors
> Dear all,
>
> What is the purpose of the --premultiply_ctf option for particle
> extraction with relion_preprocess?
>
> The help (and the code) is clear - it multiplies the micrograph by the CTF
> specified in the .star file before extraction, but what would be the
> purpose of doing this?
>
> Is this intended as a way to obtain a CTF-corrected particle stack? I’m
> confused because correction should require dividing by the CTF (or using a
> Wiener filter, etc).
>
> Thank you,
> David
--
Sjors Scheres
MRC Laboratory of Molecular Biology
Francis Crick Avenue, Cambridge Biomedical Campus
Cambridge CB2 0QH, U.K.
tel: +44 (0)1223 267061
http://www2.mrc-lmb.cam.ac.uk/groups/scheres
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