2QVO.xds: Difference between revisions

24 bytes added ,  10 November 2009
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==Optimization of data reduction==
==Optimization of data reduction==


The only safe way to optimize the data reduction is to look at external quality indicators. Internal R-factors, and even the correlation coefficient of the anomalous signal are of relatively little value. A readily available external quality indicator is CCmax/CCweak as obtained by SHELXD.
The only safe way to optimize the data reduction is to look at external quality indicators. Internal R-factors, and even the correlation coefficient of the anomalous signal are of relatively little value. A readily available external quality indicator is CCmax/CCweak as obtained by [[ccp4com:SHELX_C/D/E|SHELXD]].


One candidate for optimization is MAXIMUM_ERROR_OF_SPOT_POSITION. By default this is 3.0 . In the case of these data, this default appears to be very small, because the STANDARD DEVIATION OF SPOT    POSITION (PIXELS)  is quite high (1.5 and more). This prevents XDS from using all the reflections for geometry refinement.
One candidate for optimization is MAXIMUM_ERROR_OF_SPOT_POSITION. By default this is 3.0 . In the case of these data, this default appears to be very small, because the STANDARD DEVIATION OF SPOT    POSITION (PIXELS)  is quite high (1.5 and more). This prevents XDS from using all the reflections for geometry refinement.
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