[3dem] Low Dose Focus/Exposure

[Grassucci, Robert]

Hi Tommi
There is an option in low dose to take a defocus series.  Make sure that that is not activated.  It is designed to take an exposure at a certain defocus from where you set it in focus mode.  That would me my best guess.  Good luck.
Bob


From: 3dem [mailto:3dem-bounces at ncmir.ucsd.edu] On Behalf Of Tommi White
Sent: Monday, April 27, 2015 5:53 PM
To: 3dem at ncmir.ucsd.edu
Subject: [3dem] Low Dose Focus/Exposure

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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.ncmir.ucsd.edu/pipermail/3dem/attachments/20150427/6ba28406/attachment.html>