Index: /branches/eam_branches/ipp-pstamp-20260421/ippconfig/recipes/ppImage.config
===================================================================
--- /branches/eam_branches/ipp-pstamp-20260421/ippconfig/recipes/ppImage.config	(revision 43019)
+++ /branches/eam_branches/ipp-pstamp-20260421/ippconfig/recipes/ppImage.config	(revision 43020)
@@ -870,5 +870,5 @@
   BIN1.FITS        BOOL    TRUE            # Save 1st binned chip image?
   BIN2.FITS        BOOL    TRUE            # Save 2nd binned chip image?
-  BACKGROUND       BOOL    TRUE            # Subtract background?
+  BACKGROUND       BOOL    FALSE           # do not subtract background in normalization (used by detrend construction)
 END
 
Index: /branches/eam_branches/ipp-pstamp-20260421/ippconfig/simtest/ppImage.config
===================================================================
--- /branches/eam_branches/ipp-pstamp-20260421/ippconfig/simtest/ppImage.config	(revision 43019)
+++ /branches/eam_branches/ipp-pstamp-20260421/ippconfig/simtest/ppImage.config	(revision 43020)
@@ -161,5 +161,6 @@
   BIAS            BOOL    TRUE            # Bias subtraction
   DARK            BOOL    TRUE            # Dark subtraction
-  SHUTTER         BOOL    TRUE            # Shutter correction
+  ## shutter correction is not well tested and not used by gpc1, skip for now 
+  SHUTTER         BOOL    FALSE           # Shutter correction
   FLAT            BOOL    FALSE           # Flat-field normalisation
   MASK            BOOL    FALSE           # Mask bad pixels