Magnification Refinement

Dear All,

I am using Frealign for carrying out reconstruction of helical filaments of a reasonably large dataset. I split my data in several parts , determine the orientation with iFlag set to 1 and the termination value to negative & then combine all of them to finish the reconstruction (with iFlag set to 1 & termination value to 0).

During the course of the process I keep the Magnification refinement as T.

However with many images newly added, the process failed to find the orientation parameters of several of them. I then turned off the magnification refinement (set to F) and then the orientation search finished successfully. After carrying out the reconstruction I found out that the resulting map is worse than before.

Interestingly some of the images that failed with Magnification refinement on (T) had earlier successfully completed their run of refinement thus yielding good results.

Can you hint why this may be so ? Any possible way out if I am missing something ?

Best Wishes

Andy