Index: /trunk/ppMerge/src/ppMerge.c
===================================================================
--- /trunk/ppMerge/src/ppMerge.c	(revision 9462)
+++ /trunk/ppMerge/src/ppMerge.c	(revision 9463)
@@ -71,7 +71,7 @@
     psFree(config);
 
-    psLibFinalize();
     pmConceptsDone();
     pmConfigDone();
+    psLibFinalize();
 
 //    ppMemCheck();
Index: /trunk/ppMerge/src/ppMergeCombine.c
===================================================================
--- /trunk/ppMerge/src/ppMergeCombine.c	(revision 9462)
+++ /trunk/ppMerge/src/ppMergeCombine.c	(revision 9463)
@@ -258,4 +258,12 @@
                 }
 
+                // Set the dark time for the output image, since we normalised
+                if (options->darktime) {
+                    psMetadataItem *darkItem = psMetadataLookup(cell->concepts, "CELL.DARKTIME");
+                    darkItem->data.F32 = 1.0;
+                    psMetadataItem *expItem = psMetadataLookup(cell->concepts, "CELL.EXPOSURE");
+                    expItem->data.F32 = 1.0;
+                }
+
                 memCheck();
 #endif
Index: /trunk/ppMerge/src/ppMergeOptions.c
===================================================================
--- /trunk/ppMerge/src/ppMergeOptions.c	(revision 9462)
+++ /trunk/ppMerge/src/ppMergeOptions.c	(revision 9463)
@@ -34,5 +34,5 @@
     options->zero = false;
     options->scale = false;
-    options->exptime = false;
+    options->darktime = false;
     options->shutter = false;
     options->sample = 1;
@@ -147,25 +147,25 @@
             options->zero = false;
             options->scale = false;
-            options->exptime = false;
+            options->darktime = false;
             options->shutter = false;
         } else if (strcasecmp(type, "DARK") == 0) {
             options->zero = false;
             options->scale = false;
-            options->exptime = true;
+            options->darktime = true;
             options->shutter = false;
         } else if (strcasecmp(type, "FLAT") == 0) {
             options->zero = false;
             options->scale = true;
-            options->exptime = false;
+            options->darktime = false;
             options->shutter = false;
         } else if (strcasecmp(type, "FRINGE") == 0) {
             options->zero = true;
             options->scale = true;
-            options->exptime = false;
+            options->darktime = false;
             options->shutter = false;
         } else if (strcasecmp(type, "SHUTTER") == 0) {
             options->zero = false;
             options->scale = false;
-            options->exptime = false;
+            options->darktime = false;
             options->shutter = true;
         } else {
@@ -173,5 +173,5 @@
             options->zero = false;
             options->scale = false;
-            options->exptime = false;
+            options->darktime = false;
             options->shutter = false;
         }
@@ -180,5 +180,5 @@
         options->zero = false;
         options->scale = false;
-        options->exptime = false;
+        options->darktime = false;
     }
 
@@ -186,7 +186,7 @@
 #if 0
     // Or you can set them individually
-    OPTION_PARSE(options->zero,    config->arguments, "-zero",    Bool);
-    OPTION_PARSE(options->scale,   config->arguments, "-scale",   Bool);
-    OPTION_PARSE(options->exptime, config->arguments, "-exptime", Bool);
+    OPTION_PARSE(options->zero,     config->arguments, "-zero",    Bool);
+    OPTION_PARSE(options->scale,    config->arguments, "-scale",   Bool);
+    OPTION_PARSE(options->darktime, config->arguments, "-exptime", Bool);
 #endif
 
Index: /trunk/ppMerge/src/ppMergeOptions.h
===================================================================
--- /trunk/ppMerge/src/ppMergeOptions.h	(revision 9462)
+++ /trunk/ppMerge/src/ppMergeOptions.h	(revision 9463)
@@ -21,5 +21,5 @@
     bool zero;                          // Subtract background before combining?
     bool scale;                         // Scale by the background before combining?
-    bool exptime;                       // Normalise by the exposure time?
+    bool darktime;                      // Normalise by the dark time (time since flush)?
     bool shutter;                       // Generate shutter correction?
     unsigned int sample;                // Sampling factor for measuring the background
Index: /trunk/ppMerge/src/ppMergeScaleZero.c
===================================================================
--- /trunk/ppMerge/src/ppMergeScaleZero.c	(revision 9462)
+++ /trunk/ppMerge/src/ppMergeScaleZero.c	(revision 9463)
@@ -47,5 +47,5 @@
     assert(config);
 
-    if (!options->scale && !options->zero && !options->exptime) {
+    if (!options->scale && !options->zero && !options->darktime) {
         return true;                    // We did everything we were asked for
     }
@@ -161,11 +161,11 @@
     psStats *bgStats = psStatsAlloc(options->mean); // Statistic to measure the background
     psVector *gains = NULL;             // The gains for each cell
-    psImage *exptime = NULL;            // The exposure time for each integration of each cell
+    psImage *darktime = NULL;           // The dark time for each integration of each cell
     if (options->scale) {
         gains = psVectorAlloc(data->numCells, PS_TYPE_F32);
         gains->n = data->numCells;
     }
-    if (options->exptime) {
-        exptime = psImageAlloc(data->numCells, filenames->n, PS_TYPE_F32);
+    if (options->darktime) {
+        darktime = psImageAlloc(data->numCells, filenames->n, PS_TYPE_F32);
     }
 
@@ -199,11 +199,11 @@
 
                 // Normalising by the exposure time
-                if (options->exptime) {
-                    exptime->data.F32[i][cellNum] = psMetadataLookupF32(&mdok, cell->concepts,
-                                                                        "CELL.EXPOSURE");
-                    if (!mdok || isnan(exptime->data.F32[i][cellNum])) {
-                        psLogMsg(__func__, PS_LOG_WARN, "CELL.EXPOSURE for file %s chip %d cell %d is not "
+                if (options->darktime) {
+                    darktime->data.F32[i][cellNum] = psMetadataLookupF32(&mdok, cell->concepts,
+                                                                        "CELL.DARKTIME");
+                    if (!mdok || isnan(darktime->data.F32[i][cellNum])) {
+                        psLogMsg(__func__, PS_LOG_WARN, "CELL.DARKTIME for file %s chip %d cell %d is not "
                                  "set.\n", name, j, k);
-                        exptime->data.F32[i][cellNum] = NAN;
+                        darktime->data.F32[i][cellNum] = NAN;
                         status = false;
                     }
@@ -302,10 +302,10 @@
     }
 
-    if (options->exptime) {
+    if (options->darktime) {
         if (!options->scale) {
             // Copy over the exposure times
-            *scales = psImageCopy(*scales, exptime, PS_TYPE_F32);
+            *scales = psImageCopy(*scales, darktime, PS_TYPE_F32);
         } else {
-            *scales = (psImage*)psBinaryOp(*scales, *scales, "*", exptime);
+            *scales = (psImage*)psBinaryOp(*scales, *scales, "*", darktime);
         }
     }