[3dem] Newbie question - Defocus mistmatch
Eduardo Sanz Garcia
esanzgar at gmail.com
Fri Oct 24 17:17:15 PDT 2008
Dear 3DEM users,
Has anyone observe a mismatch between the defocus values reported by the
electron microscope software and the real defocus values computed from
Example of a pair of micrographs:
First micrograph (this one is the reference):
* Reported defocus value by the microscope: -2 microns
* Defocus value computed from the powerspectrum: -2.2 microns
I use the "series" option to change the defocus and take the other
* Reported defocus value by the microscope: -4 microns
* Defocus value computed from the powerspectrum: *-2.6* microns
(here is the problem, it should be closer to -4 microns).
We use a Tecnai F30.
Is this a problem of hysteresis?
Thank you very much.
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