Index: trunk/psModules/src/camera/pmFPAMaskWeight.c
===================================================================
--- trunk/psModules/src/camera/pmFPAMaskWeight.c	(revision 31451)
+++ trunk/psModules/src/camera/pmFPAMaskWeight.c	(revision 35038)
@@ -538,8 +538,9 @@
     psF32 **imageData = readout->image->data.F32;// Dereference image
     psF32 **varianceData = readout->variance ? readout->variance->data.F32 : NULL; // Dereference variance map
-
+    float maskFrac = 0.0;
     for (int y = 0; y < numRows; y++) {
         for (int x = 0; x < numCols; x++) {
             if (maskData[y][x] & maskVal) {
+  	        maskFrac += 1;
                 imageData[y][x] = NAN;
                 if (varianceData) {
@@ -549,5 +550,7 @@
         }
     }
-
+    maskFrac = maskFrac / (1.0 * numRows * numCols);
+    psMetadataAddF32(readout->analysis, PS_LIST_TAIL, "READOUT.MASK.FRAC", PS_META_REPLACE,
+		     "fraction of pixels masked by pmReadoutMaskApply",maskFrac);
     return true;
 }