Index: trunk/psModules/src/camera/pmFPAMaskWeight.c
===================================================================
--- trunk/psModules/src/camera/pmFPAMaskWeight.c	(revision 20489)
+++ trunk/psModules/src/camera/pmFPAMaskWeight.c	(revision 20685)
@@ -491,8 +491,8 @@
     for (int i = 0; i < num; i++) {
         float measuredSig = PS_SQR(source->data.F32[i] / stdev); // Measured significance
-        if (source->data.F32[i] <= 0.0) {
+        ratio->data.F32[i] = guess->data.F32[i] / measuredSig;
+        if (source->data.F32[i] <= 0.0 || !isfinite(ratio->data.F32[i])) {
             photMask->data.PS_TYPE_MASK_DATA[i] = 0xFF;
         }
-        ratio->data.F32[i] = guess->data.F32[i] / measuredSig;
         psTrace("psModules.camera", 9, "Ratio %d: %f, %f, %f\n",
                 i, guess->data.F32[i], measuredSig, ratio->data.F32[i]);