Index: trunk/ppImage/src/ppImageDetrendReadout.c
===================================================================
--- trunk/ppImage/src/ppImageDetrendReadout.c	(revision 26644)
+++ trunk/ppImage/src/ppImageDetrendReadout.c	(revision 26653)
@@ -27,4 +27,7 @@
 	  psAssert(item, "Should be there!");
 	  item->data.F32 = 1.0;
+
+	  // for unity gain, there is no modification for the readnoise, note that it has (effectively) been updated
+	  psMetadataRemoveKey(input->parent->concepts, "CELL.READNOISE.UPDATE");
 	} else {
 	  psWarning("CELL.GAIN is NAN for readout (%d,%d,%d), image will be masked.", view->chip, view->cell, view->readout);