Magnification questions

Submitted by Awesome Xu on Thu, 2015-12-24 07:08

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Magdistortion

Hi, I am trying to correct micrographs collected from K2 Summit using mag_distortion serial programs. But I have faced some problems about magdistortion.
1. Can the micrographs (not crystalline areas, such as virus or proteins) be used for distortion estimation? I have tested some images from different types of grids with various samples. It seems that the major scale and minor scale are the same in the same batch of micrographs. But the distortion angles are quite different in the same batch.
2. If the micrographs collected can be used for distortion estimation. What's the optimal resolution shell for estimation process?

Thanks,
JW Xu

timgrant Sat, 2015-12-26 16:40

Hi,

1. Using the mag_distortion_estimate program, then you can only use samples that when a number of images are summed in Fourier space, produce a ring. This would typically done by averaging the tranforms of a number of different crystals in lots of different orientations, such as from images of gold on a cross grating. This means that images of sample cannot themselves be used for the estimation with the program, however if you have a number of images which contain crystalline ice, then you may be able to use those.

2. The resolution shells to use depend on the spatial frequency of the ring. The program defaults should work for gold, but you can change them to fit around other frequencies if you use something other than gold. The program outputs a masked amplitude spectrum, you should check to see that the ring is seen clearly in this image, if it is being masked, then you will need to change the frequencies.

Cheers,

Tim