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Xscale: Difference between revisions
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== Simple and advanced usage == | == Simple and advanced usage == | ||
[http://www.mpimf-heidelberg.mpg.de/~kabsch/xds/html_doc/xscale_parameters.html XSCALE] is the scaling program of the XDS suite. It scales reflection files (typically called XDS_ASCII.HKL) produced by XDS. Since the CORRECT step of XDS already scales an individual dataset, XSCALE is only ''needed'' if several datasets should be scaled relative to another. However, it does not deterioriate a dataset if it is "scaled again" in XSCALE, since the supporting points of the scalefactors are at the same positions in detector and batch space. | [http://www.mpimf-heidelberg.mpg.de/~kabsch/xds/html_doc/xscale_parameters.html XSCALE] is the scaling program of the XDS suite. It scales reflection files (typically called XDS_ASCII.HKL) produced by XDS. Since the CORRECT step of XDS already scales an individual dataset, XSCALE is only ''needed'' if several datasets should be scaled relative to another. However, it does not deterioriate a dataset if it is "scaled again" in XSCALE, since the supporting points of the scalefactors are at the same positions in detector and batch space. | ||
One advantage of using XSCALE for a single dataset is that the user can specify the limits of the resolution shells. Another is that zero-dose extrapolation can be done. | |||
At the XDS website, there is a short and a long commented example of [http://www.mpimf-heidelberg.mpg.de/~kabsch/xds/html_doc/INPUT_templates/XSCALE.INP XSCALE.INP] | At the XDS website, there is a short and a long commented example of [http://www.mpimf-heidelberg.mpg.de/~kabsch/xds/html_doc/INPUT_templates/XSCALE.INP XSCALE.INP] | ||
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=== based on resolution shell and frame number === | === based on resolution shell and frame number === | ||
The usual (like in | The usual correction (like in AIMLESS and SCALEPACK) based on resolution shell and frame number is performed in [[XDS]] as part of the CORRECT step - it can be switched off by omitting DECAY from the default CORRECTIONS= DECAY MODULATION ABSORP. DECAY correction is also the default in XSCALE. | ||
It is instructive to inspect DECAY.cbf (using "XDS-Viewer DECAY.cbf"). This visualizes the scale factors employed by the CORRECT step (the equivalent files from XSCALE are called DECAY_*.cbf); the right sidebar gives the mapping between shades of gray, and numbers (1000 corresponds to a scalefactor of 1). Along the horizontal axis the frame number (or rather the batch number) is shown, along the vertical axis the resolution shell. | It is instructive to inspect DECAY.cbf (using "XDS-Viewer DECAY.cbf"). This visualizes the scale factors employed by the CORRECT step (the equivalent files from XSCALE are called DECAY_*.cbf); the right sidebar gives the mapping between shades of gray, and numbers (1000 corresponds to a scalefactor of 1). Along the horizontal axis the frame number (or rather the batch number) is shown, along the vertical axis the resolution shell. | ||
=== for individual reflections === | === for individual reflections: zero-dose extrapolation === | ||
To "switch on" radiation damage correction of individual reflections ([http://dx.doi.org/10.1107/S0907444903006516 K. Diederichs, S. McSweeney and R. B. G. Ravelli (2003) Zero-dose extrapolation as part of macromolecular synchrotron data reduction. ''Acta Cryst.'' '''D59''', 903-909]) it suffices to use the CRYSTAL_NAME keyword. '''The CRYSTAL_NAME parameters of different datasets do not have to be different'''. If they are different, this results in more degrees of freedom (namely, the slopes of the reflection intensity as a function of dose) for the program to fit the observed changes of intensities which are induced by radiation damage. However, if the datasets are based on the same crystal, or the datasets are based on crystals from the same drop, it is reasonable to assume that the slopes are the same. | To "switch on" radiation damage correction of individual reflections ([http://dx.doi.org/10.1107/S0907444903006516 K. Diederichs, S. McSweeney and R. B. G. Ravelli (2003) Zero-dose extrapolation as part of macromolecular synchrotron data reduction. ''Acta Cryst.'' '''D59''', 903-909]) it suffices to use the CRYSTAL_NAME keyword. '''The CRYSTAL_NAME parameters of different datasets do not have to be different'''. If they are different, this results in more degrees of freedom (namely, the slopes of the reflection intensity as a function of dose) for the program to fit the observed changes of intensities which are induced by radiation damage. However, if the datasets are based on the same crystal, or the datasets are based on crystals from the same drop, it is reasonable to assume that the slopes are the same. | ||