Interpretation of global CTF residual

CTF Estimation
1

Hi all,

I have an apoferritin dataset collected on one of our scopes which has substantial beam tilt (estimated at ~1.2mrad total). Correcting for this and trefoil/tetra etc improves resolution a lot - from 2.8 to 1.9 - but looking at the log for global CTF fitting, it seems that there is still rather a large residual after the correction is done (see attached).

I’m not sure exactly what this implies - does this mean there is some component that cannot be modeled? any suggestions appreciated. Also to me it looks like in the even terms there is a clear symmetrical pattern which is not being modeled…

Cheers
Oli

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2

Also I’m a little confused - if I select to only refine beam tilt, it still seems to calculate values for trefoil and all the other parameters… is that expected?

3

@olibclarke I noticed that too, but the log actually states those values are not updated. Seems it always calculates all of the parameters, but only updates the ones you asked for.