Index: /trunk/psphot/src/psphotParseCamera.c
===================================================================
--- /trunk/psphot/src/psphotParseCamera.c	(revision 11172)
+++ /trunk/psphot/src/psphotParseCamera.c	(revision 11173)
@@ -24,4 +24,10 @@
     psMetadataAddS32 (recipe, PS_LIST_TAIL, "BACKGROUND.XBIN", PS_META_NO_REPLACE, "default binning",          64);
     psMetadataAddS32 (recipe, PS_LIST_TAIL, "BACKGROUND.YBIN", PS_META_NO_REPLACE, "default binning",          64);
+
+    // XXX we need to be able to distinguish several cases:
+    // 1) the particular output data was not requested
+    // 2) the particular output data was requested but was not generated (skipped)
+    // 3) the particular output data was requested but was not generated (for valid failure)
+    // 4) the particular output data was requested but was not generated (surprising failure)
 
     // these calls bind the I/O handle to the specified fpa