Calculate defocus at different coordinates with output from patch CTF correction

Hi All,

I’m currently trying to calculate defocus values at different spots in my micrograph using the output from a patched CTF job. Normally this can be done with a regular CTF extraction job but I would like to do it outside of cryosparc.

It seems the key is using the matrix from the “_ctf_spline.npy” file. For a 4x4 knots patched CTF job, the output is a 4x4 matrix. But I’m not sure what this matrix means and am having a hard time reproducing the result of CTF extraction job.

Could anyone shed some light on how to use the output from a patched CTF job to find the defocus value at any given coordinate?

Thanks in advance for any help,