Index: /trunk/MagicSoft/Mars/mcalib/MCalibrationChargePix.cc
===================================================================
--- /trunk/MagicSoft/Mars/mcalib/MCalibrationChargePix.cc	(revision 3683)
+++ /trunk/MagicSoft/Mars/mcalib/MCalibrationChargePix.cc	(revision 3684)
@@ -659,5 +659,5 @@
 //
 // Calculate the total F-Factor with the formula:
-//   fMeanFFactorFADC2Phot = Sqrt ( fRSigmaSquare / GetMeanSquare() ) * nphotons
+//   fMeanFFactorFADC2Phot = Sqrt ( fRSigmaSquare ) / GetMean()  * sqrt( nphotons )
 //
 // Calculate the error of the total F-Factor
@@ -678,5 +678,5 @@
     }
 
-  fMeanFFactorFADC2Phot =  TMath::Sqrt(fRSigmaSquare) / GetMean() * nphotons;
+  fMeanFFactorFADC2Phot =  TMath::Sqrt(fRSigmaSquare * nphotons) / GetMean() ;
   
   if (fMeanFFactorFADC2Phot < 0.)
@@ -688,5 +688,5 @@
   const Float_t ffactorrelvar = 0.25 * fRSigmaSquareVar / ( fRSigmaSquare * fRSigmaSquare) 
                               + GetMeanRelVar() 
-                              + nphotonsrelvar;
+                              + 0.25 * nphotonsrelvar;
   
   fMeanFFactorFADC2PhotVar    = ffactorrelvar * fMeanFFactorFADC2Phot * fMeanFFactorFADC2Phot;