[3dem] [ccpem] on the meaning of fourier shell ofFSC

Marin van Heel marin.vanheel at googlemail.com
Thu Dec 10 05:49:35 PST 2015

On 09/12/2015 02:32, Smith Lee wrote:
> Dear All,
> Will you please explain to me in plain language on the meaning of 
> fourier shell in the term "fourier shell correlation (FSC)?
> Smith

Dear Smith

The meaning of "Fourier Shell" or "Fourier Ring" in the definition of 
the FSC or of the FRC respectively is clearly explained in the first 
publications on the issue (see below). The "Fourier Ring", is a circular 
area in 2D Fourier space with an inner radius and an outer radius which 
typically has the width "1" . The "Fourier Shell" is a spherical volume 
mask in Fourier space with an inner radius and an outer radius, again 
with a typical width of "1". The FRC and FSC have become
the "gold standard" quality metrics for measuring reproducible 
resolution in electron microscopy,  but are now also used outside the 
field of single-particle cryo EM (X-ray crystallography, light 
microscopy, for example).  If you have a problem finding these old 
papers please request the PDFs from me directly. (You may also want have 
a look at the Wikipedia page: 
https://en.wikipedia.org/wiki/Fourier_shell_correlation ).



Harauz, G.; van Heel M "Exact filters for general geometry three 
dimensional reconstruction". /Optik/ *73* (1986) 146–156

van Heel, M.; Keegstra, W.; Schutter, W.; van Bruggen E.F.J. (1982). 
/Arthropod hemocyanin studies by image analysis, in: Structure and 
Function of Invertebrate Respiratory Proteins,EMBO Workshop 1982, E.J. 
Wood/. /Life Chemistry Reports/. Suppl. 1. pp. 69–73. ISBN 


     Prof Dr Ir Marin van Heel

     Professor of Cryo-EM Data Processing

     Leiden University
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     Emeritus Professor of Structural Biology

     Imperial College London
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