Index: trunk/ppStack/src/ppStackSources.c
===================================================================
--- trunk/ppStack/src/ppStackSources.c	(revision 41529)
+++ trunk/ppStack/src/ppStackSources.c	(revision 42094)
@@ -341,7 +341,9 @@
             options->norm = psVectorAlloc(num, PS_TYPE_F32);
             for (int i = 0; i < num; i++) {
-	      if (!isfinite(trans->data.F32[i])) {
-		continue;
-	      }
+		if (!isfinite(trans->data.F32[i])) {
+		    psLogMsg("ppStack", PS_LOG_INFO, "Non-finite transparency, skipping correction for image %d: %f mag (%f) (with inputMask value %d)\n",
+			     i, NAN, trans->data.F32[i], inputMask->data.U8[i]);
+		    continue;
+		}
                 psArray *sources = sourceLists->data[i]; // Sources of interest
                 float magCorr = zp->data.F32[i] - trans->data.F32[i] - 2.5*log10(options->sumExposure) - airmassTerm * airmassTarget;