Content:

Introduction

By default, autoPROC will let XDS integrate over the whole detector area (apart from module gaps or masked regions due to beamstop or high- and low-resolution limits). From version after June 2015, the detection and (if adequate) exclusion of ice-rings is the default in autoPROC.

It might often be a good idea to integrate images once with and once without excluding those ice-ring regions: it is not always clear which effect (not having any measurements in certain thin shells or having potentially poorly integrated values there) has a more detrimental effect on the usage scenario (heavy-atom detection, experimental phasing, molecular replacement or refinement).

For an example covering refinement see the BUSTER CC-plot page.

Should I ... or should I not?

After running autoPROC, two files can give an indication of the presence of ice-rings:

SPOT.noHKL.png

This shows spots from all images used during indexing that could not be indexed. Ice-rings can show up very clearly: SPOT.noHKL.png

xds_spots2res.log

The automatic analysis of un-indexed spots is listed: 

 Resolution [A] :  no. of spots
------------------------------------------------------------------------------
  3.90 -   3.88 :       1738 spots with score=      6.437    known ice-ring resolution
  3.66 -   3.65 :       1479 spots with score=      8.217    known ice-ring resolution
  3.44 -   3.43 :       1734 spots with score=      9.633    known ice-ring resolution
  2.99 -   2.89 :        144 spots with score=      0.145  
  2.87 -   2.28 :       2807 spots with score=      0.520  
  2.26 -   2.14 :       3231 spots with score=      2.762  
  2.12 -   2.04 :       2383 spots with score=      2.942    known ice-ring resolution
  1.95 -   1.94 :        229 spots with score=      1.272    known ice-ring resolution
  1.91 -   1.91 :       1097 spots with score=     12.189    known ice-ring resolution
  1.88 -   1.88 :        202 spots with score=      2.244    known ice-ring resolution
  1.72 -   1.72 :         35 spots with score=      0.389    known ice-ring resolution

Excluding ice-rings during processing

Ice-rings will be excluded by default (if detectable). This corresponds to running with the XdsExcludeIceRingsAutomatically=yes parameter. The effect can be seen in the file XDS.INP - if there are any ice-rings. In cases where the automatic detection seems to miss some real ice-rings (because they don't follow our basic assumptions), you can run with 

% process XdsExcludeIceRingsAutomatically=all ...

to exclude all known ice-ring resolutions (up to 1.123A) independently of a successful analysis and detection.

To switch of th exclusion of ice-rings (as it became the default in releases after June 2015) one would run 

% process XdsExcludeIceRingsAutomatically=no ...

Parameters affecting ice-ring detection

Some parameters will change the way ice-rings are automatically detected; these could be given on the commandline or placed into a specific macro.

Xds_Spot2Res_MinSpot2 (default=20)

sets the minimum required number of un-indexed spot within a resolution shell to consider it for ice-ring definition

Xds_Spot2Res_Prec (default=0.01)

defines the precision (significant digits) for resolution shells: a smaller value like 0.001 could split a broader ice-ring into several smaller ones - but would also minmize the actually excluded detector ring.