[3DEM] Why FEG?

[Henning Stahlberg]

Hi,

The biggest difference between a FEG and an LaB6 performance seems to 
me to arise from the effective electron source opening angle, when 
short cryoEM exposure times are considered. I used 0.1 mrad for a FEG 
and 0.7 mrad for a thermal electron source, see also Jong & van Dyck, 
Ultramicroscopy 49, 66-80 (1993).
http://dx.doi.org/10.1016/0304-3991(93)90213-H

Even when only interested in 0.5 nm resolution, the difference is 
significant, see
http://www.amp.ucdavis.edu/index.php?p=download

Those are CTF simulations made with a simple MS-Excel sheet, which is 
also on that server.

Henning.


Henning Stahlberg, Ph.D.,
Molecular & Cellular Biology, Briggs Hall 115B,
UC-Davis, 1 Shields Ave., Davis, CA 95616, USA
Tel: +1 (530) 752 82 82      Fax: +1 (530) 752 30 85
mailto:HStahlberg at ucdavis.edu	
http://www.amp.ucdavis.edu	
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On Apr 23, 2004, at 1:43 AM, Philip Koeck wrote:

> Hi,
>
>  
>
> I’ve been playing around with Max Sidorow's CTFexplorer and I’m 
> finding it hard to see the
> advantage of FEG microscopes for structural biology.
>
> At 61000-times magnification I can’t see any major difference between 
> the Tecnai 20T and
> the Tecnai F20T for example.
>
> Only at magnifications beyond 300000 is the F20T clearly superior (due 
> to better spatial
> coherence).
>
>  
>
> Am I (or is CTFexplorer) missing something relevant?
>
>  
>
> The CTFexplorer can be found at http://clik.to/ctfexplorer.
>
> Upon request I can also send a Word file with the CTF-plots.
>
>  
>
> Philip
>
>