Index: trunk/psModules/src/imcombine/pmSubtraction.h
===================================================================
--- trunk/psModules/src/imcombine/pmSubtraction.h	(revision 29004)
+++ trunk/psModules/src/imcombine/pmSubtraction.h	(revision 29601)
@@ -20,4 +20,11 @@
 #include <pmSubtractionKernels.h>
 #include <pmSubtractionStamps.h>
+
+// if we use the original ppSub implementation, we subtract a central delta-function for all
+// kernels to for a zero integral.  in the Alard-Lupton style zeroing, we can either subtract a
+// Gaussian from all kernels (ZERO_KERNEL_ZERO_FLUX), or we can subtract it from all but the
+// first kernel.
+# define CENTRAL_DELTA 0
+# define ZERO_KERNEL_ZERO_FLUX 1
 
 /// @addtogroup imcombine Image Combinations