[3dem] Low Dose Focus/Exposure

Tommi White whitetommi at gmail.com
Mon Apr 27 14:52:30 PDT 2015


Dear 3DEM.

Perhaps the community can assist with this issue we are struggling with.
In Low Dose on our Tecnai F30, the Low Dose focus image has a different
defocus value (using FFT) versus Low Dose Exposure.

I have been checking this on a relatively flat cross-grating (not cryo)
specimen.  I set LD exposure to be zero defocus (with focus knob), but when
I switch over to LD focus (~ 3 micron away on tilt axis) the image is
defocused (~ -2 micron).

I believe there is some 200 kV procedure alignment that must not be set
properly - but am not quite sure which one...any suggestions on what to
tweak to get this exposure/focus area reflecting the same defocus?

Thanks for any suggestions...
Tommi

Tommi A. White, Ph.D.
Associate Director, Electron Microscopy Core Facility
Assistant Professor of Biochemistry
University of Missouri
W125 Veterinary Medicine
Columbia, MO 65211
573-882-8304
http://emc.missouri.edu
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