Index: trunk/psphot/src/psphotModelBackground.c
===================================================================
--- trunk/psphot/src/psphotModelBackground.c	(revision 20769)
+++ trunk/psphot/src/psphotModelBackground.c	(revision 20770)
@@ -145,5 +145,5 @@
             // convert the ruff grid cell to the equivalent fine grid cell
             // XXX we need to watch out for row0,col0
-            ruffRegion = psRegionSet (ix, ix + 2, iy, iy + 2);
+            ruffRegion = psRegionSet (ix, ix + 1, iy, iy + 1);
             fineRegion = psImageBinningSetFineRegion (binning, ruffRegion);
             fineRegion = psRegionForImage (image, fineRegion);