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Low dose data: Difference between revisions
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(change text to use DATA_RANGE_FIXED_SCALE_FACTOR instead of FIXED_SCALE_FACTOR) |
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The background counts per pixel are printed in INIT.LP, or can be estimated by visualizing the frames with [[XDS-Viewer]] or [[adxv]]. | The average of the background counts per pixel are printed in INIT.LP, or can be estimated by visualizing the frames with [[XDS-Viewer]] or [[adxv]]. | ||
In XDS, the background of a data frame is used for scaling adjacent frames relative to each other in the INTEGRATE step. | |||
This seems to work very well down to an average of 0.5 counts/pixel. If, however, the crystal is exposed so shortly/weakly that the average drops significantly below this value, scaling becomes impossible - the ratio of averages which are around zero is obviously undefined. The keyword [http://homes.mpimf-heidelberg.mpg.de/~kabsch/xds/html_doc/xds_parameters.html#DATA_RANGE_FIXED_SCALE_FACTOR== DATA_RANGE_FIXED_SCALE_FACTOR] has been introduced to handle this situation. | This seems to work very well down to an average of 0.5 counts/pixel. If, however, the crystal is exposed so shortly/weakly that the average drops significantly below this value, scaling becomes impossible - the ratio of averages which are around zero is obviously undefined. The keyword [http://homes.mpimf-heidelberg.mpg.de/~kabsch/xds/html_doc/xds_parameters.html#DATA_RANGE_FIXED_SCALE_FACTOR== DATA_RANGE_FIXED_SCALE_FACTOR] has been introduced to handle this situation. | ||