CTF sensitivity. How do the errors in the estimation of the CTF affect the CTF shap itself and the final reconstruction? Which are the most important CTF parameters? How do the errors in one parameter affect other parameters?. Which CTF?. 1D CTF. 1D PSD. 2D PSD and CTF. Which CTF?.
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2D PSD and CTF
What happens to the ideal CTF if I change a little bit my current estimate of the CTF parameters?
What if I change a little bit only one parameter?
Can you express this as percentages?
Sensitivity=How sensitive is the CTF to the changes in this parameter
What is the average sensitivity?
The most important for the CTF: Microscope voltage, defoci, and chromatic aberration
The most important for the PSD: Background parameters, microscope voltage and defoci
The most important for the first zero: Microscope voltage, defoci, and fraction of scattered electrons
These accuracies have been estimated by bootstrapping on the PSD values of a micrograph and reestimating for each subsample the CTF.
In our experiments, it did not significantly affect the phase correction
Neither the amplitude correction
Only the drift parameters, since in fact in these micrographs, there is no drift!!
The rest are insensitive (you can commit relatively large errors), but that does not mean you can remove them. If you remove them, then very bad CTFs are estimated
There are groups of parameters and changes in one parameter can be compensated by others. For instance, in the following table we see that changes in the major defocus are negatively correlated to changes in the scattered fraction and positively correlated to changes in the minor defocus.
These results have been achieved through the bootstrapping strayegy already described.
This is to difficult for me to understand, can you further clarify who affects who?
Of course, through factor analysis we can discover groups of parameters strongly influencing each other
Background medium freq.
Background low freq.
CTF decay due to incoherence
Background low freq.
CTF decay due to energy spread