Low dose data: Difference between revisions
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In XDS, the background of a data frame is used for scaling adjacent frames relative to each other in the INTEGRATE step. | 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 well down to an average of 0.05 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:// | This seems to work well down to an average of 0.05 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://xds.mpimf-heidelberg.mpg.de/html_doc/xds_parameters.html#DATA_RANGE_FIXED_SCALE_FACTOR== DATA_RANGE_FIXED_SCALE_FACTOR] has been introduced to handle this situation. | ||
See also: [[Difficult datasets]] | See also: [[Difficult datasets]] | ||
Latest revision as of 11:28, 22 October 2019
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 well down to an average of 0.05 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 DATA_RANGE_FIXED_SCALE_FACTOR has been introduced to handle this situation.
See also: Difficult datasets