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Re: Resolution as an indicator of data completeness

  • To: Brian McMahon <bm@iucr.org>
  • Subject: Re: Resolution as an indicator of data completeness
  • From: flack@mime.unige.ch (Howard Flack)
  • Date: Tue, 23 Dec 1997 17:33:37 +0100 (MET)
>G> I agree with Howard's comments that the treatment of Friedel opposites
>G> should be clarified.  

   Our violins seem to be in very fine tune today!

>G>I would also like to repeat a further suggestion
>G> that I made in D71.1 (discussing the Acta 97 instructions for authors)
>G> that it is illogical to define: 
>G> 
>G> data_diffrn_measured_fraction_theta_full
>G> data_diffrn_measured_fraction_theta_max
>G> 
>G> and
>G> 
>G> data_diffrn_reflns_theta_full
>G> 
>G> using the Bragg angle 'theta' rather than the resolution in Angstroms
>G> (which is how a protein crystallographer would have defined it). 
>G> Whereas the resolution gives an immediate indication of the extent of
>G> the data (and hence the data to parameter ratio), theta depends on the
>G> wavelength, which with increasing use of synchrotron data may be
>G> different for different experiments.  Indeed for Laue data the
>G> wavelength is different for each reflection and so 'theta' is useless
>G> whereas 'resolution' would still be sensible.

  I agree entirely with George on this point. 
  The wavelength still needs to be indicated where monochromatic 
  radiation is used.  

Best wishes,
  Howard

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