Index: trunk/ppStack/src/ppStackCombinePrepare.c
===================================================================
--- trunk/ppStack/src/ppStackCombinePrepare.c	(revision 27319)
+++ trunk/ppStack/src/ppStackCombinePrepare.c	(revision 27400)
@@ -10,5 +10,6 @@
 #include "ppStackLoop.h"
 
-bool ppStackCombinePrepare(pmReadout **ro, const char *name, ppStackFileList files, ppStackThreadData *stack,
+bool ppStackCombinePrepare(const char *outName, const char *expName,
+                           ppStackFileList files, ppStackThreadData *stack,
                            ppStackOptions *options, pmConfig *config)
 {
@@ -32,6 +33,9 @@
     }
 
-    pmCell *cell = pmFPAfileThisCell(config->files, view, name); // Output cell
-    *ro = pmReadoutAlloc(cell); // Output readout
+    pmCell *cell = pmFPAfileThisCell(config->files, view, outName); // Output cell
+    options->outRO = pmReadoutAlloc(cell); // Output readout
+
+    pmCell *expCell = pmFPAfileThisCell(config->files, view, expName); // Exposure cell
+    options->expRO = pmReadoutAlloc(expCell); // Output readout
 
     psFree(view);
@@ -42,5 +46,10 @@
     psImageMaskType maskBad = pmConfigMaskGet(maskBadStr, config); // Bits to mask for bad pixels
 
-    if (!pmReadoutStackDefineOutput(*ro, col0, row0, numCols, numRows, true, true, maskBad)) {
+    if (!pmReadoutStackDefineOutput(options->outRO, col0, row0, numCols, numRows, true, true, maskBad)) {
+        psError(PPSTACK_ERR_ARGUMENTS, false, "Unable to prepare output.");
+        return false;
+    }
+
+    if (!pmReadoutStackDefineOutput(options->expRO, col0, row0, numCols, numRows, true, true, 0)) {
         psError(PPSTACK_ERR_ARGUMENTS, false, "Unable to prepare output.");
         return false;