FAQ: Difference between revisions

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Revision as of 18:29, 3 October 2015

156 bytes added , 3 October 2015

/* I can see many diffraction spots in the BKGINIT.cbf when the BACKGROUND_RANGE is set default (first 5 degree images). When this value is set large (eg. 50 degree), no diffraction spots can be seen. It seems that this is a "real" background image. Bu...

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 No. The INIT step uses the first 5 degrees (by default) for a number of purposes (check out the files written by INIT !). BKGINIT.cbf is essentially used only for scaling purposes; the ''real'' background calculation just requires those frames which have the reflections that are integrated.
-=== I can see many diffraction spots in the BKGINIT.cbf when the BACKGROUND_RANGE is set default (first 5 degree images). When this value is set large (eg. 50 degree), no diffraction spots can be seen. It seems that this is a "real" background image. But both this two scenario produce nearly the same results (data statistics). Do I need to always change the BACKGROUND_RANGE so that there are no diffraction spots in the BKGINIT.cbf? ===
+=== I can see many diffraction spots in the BKGINIT.cbf when the BACKGROUND_RANGE is set default (first 5 degree images). When this value is set large (eg. 50 degree), no diffraction spots can be seen. It seems that only the large value produces a "real" background image. But both these two scenarios produce nearly the same results (data statistics). Do I need to always change the BACKGROUND_RANGE so that there are no diffraction spots in the BKGINIT.cbf? ===
-No. Again, BKGINIT.cbf is essentially used only for scaling purposes; the ''real'' background calculation just requires those frames which have the reflections that are integrated. Don't worry about BACKGROUND_RANGE; just use the default! The only reason to increase the BACKGROUND_RANGE is when you have so low background that even 5° of data produces many zero pixels in BKGINIT.cbf, but this is highly unlikely.
+No. Again, BKGINIT.cbf is used only for scaling purposes and masking the beamstop (in DEFPIX); the ''real'' background calculation just requires those frames which have the reflections that are integrated. Normally you don't worry about BACKGROUND_RANGE; just use the default! You need only increase the BACKGROUND_RANGE if you have so low background that a) even 5° of data produces many zero pixels in BKGINIT.cbf (but this is highly unlikely), or b) if shadowed parts of the detector are not visible in BKGINIT.cbf when viewed with xds-viewer.
 == COLSPOT ==