Index: trunk/psModules/src/imcombine/pmSubtraction.h
===================================================================
--- trunk/psModules/src/imcombine/pmSubtraction.h	(revision 18178)
+++ trunk/psModules/src/imcombine/pmSubtraction.h	(revision 18180)
@@ -6,6 +6,6 @@
  * @author GLG, MHPCC
  *
- * @version $Revision: 1.25 $ $Name: not supported by cvs2svn $
- * @date $Date: 2008-05-24 00:40:16 $
+ * @version $Revision: 1.26 $ $Name: not supported by cvs2svn $
+ * @date $Date: 2008-06-19 00:54:09 $
  * Copyright 2004-207 Institute for Astronomy, University of Hawaii
  */
@@ -79,4 +79,13 @@
                                   );
 
+/// Return the variance factor for a kernel
+///
+/// The variance factor allows conversion from the large-scale variance (which is what is calculated by
+/// pmSubtractionConvolve) and the small-scale (pixel-to-pixel) variance.
+float pmSubtractionVarianceFactor(const pmSubtractionKernels *kernels, ///< Kernel parameters
+                                  float x, float y, ///< Normalised position [-1,1]
+                                  bool wantDual ///< Calculate for the dual kernel?
+    );
+
 /// Generate images of the convolution kernel elements
 psArray *pmSubtractionKernelSolutions(const psVector *solution, ///< Solution vector