Background correction

Submitted by Leo on Thu, 2015-07-02 10:16

Forums

ctffind & ctftilt

Hi, when running new ctffind4 4.0.16 version we noticed that for about 10-20% of images reported good fit of thon rings is only to 15-20 A, while previously for the same data it was to about 4-5 A (with ver 4.0.10). Looking at output it is clear that the fit itself is fine between 15 to 5 A with the new version, but background correction is thrown off at low resolution, so that quality of fit goes to 0 at about 20 A. We tried to change low resolution limits from 30 A (which was working fine for 4.0.10) to between 100 and 15 A, but it only gets worse.

Reported limits of good fit are very useful diagnostics, so we would like to get back to the levels we used to get with 4.0.10.
Any suggestions appreciated.

Best,
Leonid

Alexis Thu, 2015-07-02 11:47

Hi Leonid,

Thanks a lot for taking time to report this.

Would you be able to send me one of the micrographs which throws 4.0.16 off but worked with 4.0.10? That way I can investigate what might be going on.

Thanks
Alexis

Alexis Tue, 2015-07-07 05:29

Leonid,

Thanks - I received the micrograph. Could you please give me the parameters needed to reproduce what you are seeing? Voltage, amplitude contrast, Cs, etc. perhaps even the defocus range & step size you used as well as astig tolerance.

Thanks
Alexis