[phenixbb] Implementation of French & Wilson data correction?

Pavel Afonine pafonine at lbl.gov
Fri Feb 25 10:05:39 PST 2011

  Hi Joe,

the main motivation to implement F&W based conversion of Iobs to Fobs 
was the community driven suggestion that this is a better way of 
converting Iobs to Fobs, compared to simple

if(Iobs >= 0):
Fobs = sqrt(Iobs)
Fobs = 0

that phenix.refine uses.

I'm not aware of any systematic and conclusive study demonstrating that 
one way is better or worse than the other one. Since now we have both 
options available in PHENIX this opens a good opportunity (for whoever 
who has enough of enthusiasm and time) to study this some more within 
one software framework.

Some good discussion on related subjects can be found here:

"Structure refinement: some background theory and practical strategies".
David Watkin.
J. Appl. Cryst. (2008). 41, 491–522


On 2/25/11 8:56 AM, Joseph Noel wrote:
> Hi All,
> Any pointers on implementing the new option in the latest build for 
> French & Wilson correction? Does scala output negative intensities so 
> that a proper scaling with this new option can be used? Also, what 
> column labels should be used particularly for proper treatment of 
> anomalous data? Can one use the labels output by scala?
> Joe

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