Microscopy: Why FEG?

Philip Koeck Philip.Koeck at biosci.ki.se
Tue May 25 04:11:29 PDT 2004


I thought some people might be interested in a follow-up of this
(Don't tell me if your not, just ignore me.)

I've taken some images of carbon film on our CM120 with a brand new
LaB6-filament just to get an idea of the limitations of this microscope.

I get information limits between 15 and 5 Angstrom depending on
magnification and defocus (only "biological" defocus values) and the
information limit does not improve with decreasing magnification as
suggested by CTF-explorer. In fact the opposite is true (at least for
constant exposure levels). Some similar data for a FEG would be

One thing is clear: Reaching 10 Angstrom and slightly better should not
be a problem with a well maintained LaB6 microscope.

For the details see the link "reference data for the CM120" at
http://www.csb.ki.se/users/philip/philown.html. This is a big word file
so you have to be patient when you download it.


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