diff --git a/Modules/Core/src/DataManagement/mitkLevelWindowManager.cpp b/Modules/Core/src/DataManagement/mitkLevelWindowManager.cpp
index ba7b1a49f1..bf91a77065 100644
--- a/Modules/Core/src/DataManagement/mitkLevelWindowManager.cpp
+++ b/Modules/Core/src/DataManagement/mitkLevelWindowManager.cpp
@@ -1,748 +1,742 @@
 /*===================================================================
 
 The Medical Imaging Interaction Toolkit (MITK)
 
 Copyright (c) German Cancer Research Center,
 Division of Medical and Biological Informatics.
 All rights reserved.
 
 This software is distributed WITHOUT ANY WARRANTY; without
 even the implied warranty of MERCHANTABILITY or FITNESS FOR
 A PARTICULAR PURPOSE.
 
 See LICENSE.txt or http://www.mitk.org for details.
 
 ===================================================================*/
 
 #include "mitkLevelWindowManager.h"
 #include "mitkDataStorage.h"
 #include "mitkImage.h"
 #include "mitkMessage.h"
 #include "mitkNodePredicateAnd.h"
 #include "mitkNodePredicateBase.h"
 #include "mitkNodePredicateDataType.h"
 #include "mitkNodePredicateNot.h"
 #include "mitkNodePredicateOr.h"
 #include "mitkNodePredicateProperty.h"
 #include "mitkProperties.h"
 #include "mitkRenderingModeProperty.h"
 #include <itkCommand.h>
 
 mitk::LevelWindowManager::LevelWindowManager()
   : m_DataStorage(nullptr)
   , m_LevelWindowProperty(nullptr)
   , m_AutoTopMost(true)
   , m_SelectedImages(false)
   , m_IsObserverTagSet(false)
   , m_CurrentImage(nullptr)
   , m_IsPropertyModifiedTagSet(false)
   , m_LevelWindowMutex(false)
 {
 }
 
 mitk::LevelWindowManager::~LevelWindowManager()
 {
   if (m_DataStorage.IsNotNull())
   {
     m_DataStorage->AddNodeEvent.RemoveListener(
       MessageDelegate1<LevelWindowManager, const DataNode *>(this, &LevelWindowManager::DataStorageAddedNode));
     m_DataStorage->RemoveNodeEvent.RemoveListener(
       MessageDelegate1<LevelWindowManager, const DataNode *>(this, &LevelWindowManager::DataStorageRemovedNode));
     m_DataStorage = nullptr;
   }
 
   if (m_IsPropertyModifiedTagSet && m_LevelWindowProperty.IsNotNull())
   {
     m_LevelWindowProperty->RemoveObserver(m_PropertyModifiedTag);
     m_IsPropertyModifiedTagSet = false;
   }
 
   // clear both observer maps
   this->ClearPropObserverLists();
 }
 
 void mitk::LevelWindowManager::SetDataStorage(DataStorage *ds)
 {
   if (ds == nullptr)
     return;
 
   /* remove listeners of old DataStorage */
   if (m_DataStorage.IsNotNull())
   {
     m_DataStorage->AddNodeEvent.RemoveListener(
       MessageDelegate1<LevelWindowManager, const DataNode *>(this, &LevelWindowManager::DataStorageAddedNode));
     m_DataStorage->RemoveNodeEvent.RemoveListener(
       MessageDelegate1<LevelWindowManager, const DataNode *>(this, &LevelWindowManager::DataStorageRemovedNode));
   }
 
   /* register listener for new DataStorage */
   m_DataStorage = ds; // register
   m_DataStorage->AddNodeEvent.AddListener(
     MessageDelegate1<LevelWindowManager, const DataNode *>(this, &LevelWindowManager::DataStorageAddedNode));
   m_DataStorage->RemoveNodeEvent.AddListener(
     MessageDelegate1<LevelWindowManager, const DataNode *>(this, &LevelWindowManager::DataStorageRemovedNode));
 
   this->DataStorageAddedNode(); // update us with new DataStorage
 }
 
 void mitk::LevelWindowManager::OnPropertyModified(const itk::EventObject &)
 {
   Modified();
 }
 
 void mitk::LevelWindowManager::SetAutoTopMostImage(bool autoTopMost, const DataNode *removedNode/* = nullptr*/)
 {
   m_AutoTopMost = autoTopMost;
   if (false == m_AutoTopMost)
   {
     return;
   }
 
   // deactivate other mode
   m_SelectedImages = false;
 
   if (m_IsPropertyModifiedTagSet && m_LevelWindowProperty.IsNotNull())
   {
     m_LevelWindowProperty->RemoveObserver(m_PropertyModifiedTag);
     m_IsPropertyModifiedTagSet = false;
   }
 
   // find topmost image in the data storage
   if (m_DataStorage.IsNull())
   {
     itkExceptionMacro("DataStorage not set");
   }
 
   DataNode::Pointer topLevelNode;
-  int maxLayer = itk::NumericTraits<int>::min();
+  int maxVisibleLayer = itk::NumericTraits<int>::min();
   m_LevelWindowProperty = nullptr;
+  m_CurrentImage = nullptr;
 
-  DataStorage::SetOfObjects::ConstPointer all = this->GetRelevantNodes();
+  DataStorage::SetOfObjects::ConstPointer all = GetRelevantNodes();
   for (DataStorage::SetOfObjects::ConstIterator it = all->Begin(); it != all->End(); ++it)
   {
     DataNode::Pointer node = it->Value();
     if (node.IsNull() || (removedNode != nullptr && node == removedNode))
+    {
       continue;
+    }
 
     m_LevelWindowMutex = true;
     node->SetBoolProperty("imageForLevelWindow", false);
     m_LevelWindowMutex = false;
 
     if (node->IsVisible(nullptr) == false)
+    {
       continue;
+    }
 
-    int layer = 0;
+    int layer = -1;
     node->GetIntProperty("layer", layer);
-    if (layer < maxLayer)
+    if (layer < maxVisibleLayer)
+    {
       continue;
+    }
 
     LevelWindowProperty::Pointer levelWindowProperty =
       dynamic_cast<LevelWindowProperty *>(node->GetProperty("levelwindow"));
     if (levelWindowProperty.IsNull())
+    {
       continue;
+    }
 
     int nonLvlWinMode1 = RenderingModeProperty::LOOKUPTABLE_COLOR;
     int nonLvlWinMode2 = RenderingModeProperty::COLORTRANSFERFUNCTION_COLOR;
 
     RenderingModeProperty::Pointer mode =
       dynamic_cast<RenderingModeProperty *>(node->GetProperty("Image Rendering.Mode"));
 
     if (mode.IsNotNull())
     {
       int currMode = mode->GetRenderingMode();
       if (currMode == nonLvlWinMode1 || currMode == nonLvlWinMode2)
       {
         continue;
       }
     }
     else
+    {
       continue;
+    }
 
     m_LevelWindowProperty = levelWindowProperty;
-    m_CurrentImage = dynamic_cast<Image *>(node->GetData());
     topLevelNode = node;
-
-    maxLayer = layer;
-  }
-
-  if (topLevelNode.IsNotNull())
-  {
-    m_LevelWindowMutex = true;
-    topLevelNode->SetBoolProperty("imageForLevelWindow", true);
-    m_LevelWindowMutex = false;
+    maxVisibleLayer = layer;
   }
 
-  this->SetLevelWindowProperty(m_LevelWindowProperty);
+  // this will set the "imageForLevelWindow" property and the 'm_CurrentImage' and call 'Modified()'
+  SetLevelWindowProperty(m_LevelWindowProperty);
 
   if (m_LevelWindowProperty.IsNull())
   {
     Modified();
   }
-  // else SetLevelWindowProperty will call Modified();
 }
 
 void mitk::LevelWindowManager::SetSelectedImages(bool selectedImages, const DataNode *removedNode/* = nullptr*/)
 {
   m_SelectedImages = selectedImages;
   if (false == m_SelectedImages)
   {
     return;
   }
 
   // deactivate other mode
   m_AutoTopMost = false;
 
   if (m_IsPropertyModifiedTagSet && m_LevelWindowProperty.IsNotNull())
   {
     m_LevelWindowProperty->RemoveObserver(m_PropertyModifiedTag);
     m_IsPropertyModifiedTagSet = false;
   }
 
   // find selected images in the data storage
   if (m_DataStorage.IsNull())
   {
     itkExceptionMacro("DataStorage not set");
   }
 
   DataNode::Pointer lastSelectedNode;
   m_LevelWindowProperty = nullptr;
+  m_CurrentImage = nullptr;
 
   DataStorage::SetOfObjects::ConstPointer all = GetRelevantNodes();
   for (DataStorage::SetOfObjects::ConstIterator it = all->Begin(); it != all->End(); ++it)
   {
     DataNode::Pointer node = it->Value();
     if (node.IsNull() || node == removedNode)
     {
       continue;
     }
 
     m_LevelWindowMutex = true;
     node->SetBoolProperty("imageForLevelWindow", false);
     m_LevelWindowMutex = false;
 
     bool selected = node->IsSelected();
     if (false == selected)
     {
       continue;
     }
 
     LevelWindowProperty::Pointer levelWindowProperty =
       dynamic_cast<LevelWindowProperty *>(node->GetProperty("levelwindow"));
     if (levelWindowProperty.IsNull())
     {
       continue;
     }
 
-    m_LevelWindowMutex = true;
-    node->SetBoolProperty("imageForLevelWindow", true);
-    m_LevelWindowMutex = false;
     int nonLvlWinMode1 = RenderingModeProperty::LOOKUPTABLE_COLOR;
     int nonLvlWinMode2 = RenderingModeProperty::COLORTRANSFERFUNCTION_COLOR;
 
     RenderingModeProperty::Pointer mode =
       dynamic_cast<RenderingModeProperty *>(node->GetProperty("Image Rendering.Mode"));
 
     if (mode.IsNotNull())
     {
       int currMode = mode->GetRenderingMode();
       if (currMode == nonLvlWinMode1 || currMode == nonLvlWinMode2)
       {
         continue;
       }
     }
     else
     {
       continue;
     }
 
     m_LevelWindowProperty = levelWindowProperty;
-    m_CurrentImage = dynamic_cast<Image*>(node->GetData());
     lastSelectedNode = node;
   }
 
+  // this will set the "imageForLevelWindow" property and the 'm_CurrentImage' and call 'Modified()'
   SetLevelWindowProperty(m_LevelWindowProperty);
 
   if (m_LevelWindowProperty.IsNull())
   {
     Modified();
   }
 }
 
 void mitk::LevelWindowManager::SetLevelWindowProperty(LevelWindowProperty::Pointer levelWindowProperty)
 {
   if (levelWindowProperty.IsNull())
   {
     return;
   }
 
   // find data node that belongs to the property
   DataStorage::SetOfObjects::ConstPointer all = m_DataStorage->GetAll();
   mitk::DataNode::Pointer propNode = nullptr;
   for (DataStorage::SetOfObjects::ConstIterator it = all->Begin(); it != all->End(); ++it)
   {
     DataNode::Pointer node = it.Value();
     LevelWindowProperty::Pointer property = dynamic_cast<LevelWindowProperty *>(node->GetProperty("levelwindow"));
     if (property == levelWindowProperty)
     {
       propNode = node;
     }
     else
     {
       m_LevelWindowMutex = true;
       node->SetBoolProperty("imageForLevelWindow", false);
       m_LevelWindowMutex = false;
     }
   }
 
   if (propNode.IsNull())
   {
     mitkThrow() << "No Image in the data storage that belongs to level-window property " << m_LevelWindowProperty;
   }
 
   if (m_IsPropertyModifiedTagSet) // remove listener for old property
   {
     m_LevelWindowProperty->RemoveObserver(m_PropertyModifiedTag);
     m_IsPropertyModifiedTagSet = false;
   }
 
   m_LevelWindowProperty = levelWindowProperty;
 
   itk::ReceptorMemberCommand<LevelWindowManager>::Pointer command =
     itk::ReceptorMemberCommand<LevelWindowManager>::New(); // register listener for new property
   command->SetCallbackFunction(this, &LevelWindowManager::OnPropertyModified);
   m_PropertyModifiedTag = m_LevelWindowProperty->AddObserver(itk::ModifiedEvent(), command);
   m_IsPropertyModifiedTagSet = true;
 
   m_CurrentImage = dynamic_cast<Image *>(propNode->GetData());
 
   m_LevelWindowMutex = true;
   propNode->SetBoolProperty("imageForLevelWindow", true);
   m_LevelWindowMutex = false;
 
   this->Modified();
 }
 
 // returns the current mitkLevelWindowProperty object from the image that is affected by changes
 mitk::LevelWindowProperty::Pointer mitk::LevelWindowManager::GetLevelWindowProperty()
 {
   return m_LevelWindowProperty;
 }
 
 // returns Level/Window values for the current image
 const mitk::LevelWindow &mitk::LevelWindowManager::GetLevelWindow()
 {
   if (m_LevelWindowProperty.IsNotNull())
   {
     return m_LevelWindowProperty->GetLevelWindow();
   }
   else
   {
     itkExceptionMacro("No LevelWindow available!");
   }
 }
 
 // sets new Level/Window values and informs all listeners about changes
 void mitk::LevelWindowManager::SetLevelWindow(const LevelWindow &levelWindow)
 {
   if (m_LevelWindowProperty.IsNotNull())
   {
     m_LevelWindowProperty->SetLevelWindow(levelWindow);
   }
   this->Modified();
 }
 
 void mitk::LevelWindowManager::DataStorageAddedNode(const DataNode *)
 {
   // update observers with new data storage
   UpdateObservers();
 
   // Initialize LevelWindowsManager to new image
   SetAutoTopMostImage(true);
 
   // check if everything is still ok
   if ((m_ObserverToVisibleProperty.size() != m_ObserverToLayerProperty.size()) ||
       (m_ObserverToLayerProperty.size() != this->GetRelevantNodes()->size()))
   {
     mitkThrow() << "Wrong number of observers in Level Window Manager!";
   }
 }
 
 void mitk::LevelWindowManager::DataStorageRemovedNode(const DataNode *removedNode)
 {
-  // first: check if deleted node is part of relevant nodes. If not, abort method because there is no need change
-  // anything.
-  if ((this->GetRelevantNodes()->size() == 0))
-    return;
+  // First: check if deleted node is part of relevant nodes.
+  // If not, abort method because there is no need change anything.
   bool removedNodeIsRelevant = false;
-  /* Iterator code: is crashing, don't know why... so using for loop
-  for (DataStorage::SetOfObjects::ConstIterator it = this->GetRelevantNodes()->Begin();
-       it != this->GetRelevantNodes()->End();
-       ++it)
-  {if (it->Value() == removedNode) {removedNodeIsRelevant=true;}}*/
-  for (unsigned int i = 0; i < this->GetRelevantNodes()->size(); i++)
-  {
-    if (this->GetRelevantNodes()->at(i) == removedNode)
+  DataStorage::SetOfObjects::ConstPointer relevantNodes = GetRelevantNodes();
+  for (DataStorage::SetOfObjects::ConstIterator it = relevantNodes->Begin(); it != relevantNodes->End(); ++it)
+  {
+    if (it->Value() == removedNode)
     {
       removedNodeIsRelevant = true;
     }
   }
-  if (!removedNodeIsRelevant)
+
+  if (false == removedNodeIsRelevant)
+  {
     return;
   }
 
   // remember node which will be removed
   m_NodeMarkedToDelete = removedNode;
 
   // update observers
   UpdateObservers();
 
   // search image that belongs to the property
   if (m_LevelWindowProperty.IsNull())
   {
     SetAutoTopMostImage(true, removedNode);
   }
   else
   {
     NodePredicateProperty::Pointer property = NodePredicateProperty::New("levelwindow", m_LevelWindowProperty);
     DataNode *n = m_DataStorage->GetNode(property);
     if (n == nullptr || m_AutoTopMost) // if node was deleted, change our behavior to AutoTopMost, if AutoTopMost is true
                                     // change level window to topmost node
     {
       SetAutoTopMostImage(true, removedNode);
     }
   }
 
   // reset variable
   m_NodeMarkedToDelete = nullptr;
 
   // check if everything is still ok
   if ((m_ObserverToVisibleProperty.size() != m_ObserverToLayerProperty.size()) ||
-      (m_ObserverToLayerProperty.size() != (this->GetRelevantNodes()->size() - 1)))
+      (m_ObserverToLayerProperty.size() != (relevantNodes->size() - 1)))
   {
     mitkThrow() << "Wrong number of observers in Level Window Manager!";
   }
 }
 
 void mitk::LevelWindowManager::UpdateObservers()
 {
-  this->ClearPropObserverLists(); // remove old observers
+  ClearPropObserverLists(); // remove old observers
   CreatePropObserverLists();      // create new observer lists
 }
 
 int mitk::LevelWindowManager::GetNumberOfObservers()
 {
   return m_ObserverToVisibleProperty.size();
 }
 
 mitk::DataStorage *mitk::LevelWindowManager::GetDataStorage()
 {
   return m_DataStorage.GetPointer();
 }
 
 bool mitk::LevelWindowManager::IsAutoTopMost()
 {
   return m_AutoTopMost;
 }
 
 bool mitk::LevelWindowManager::IsSelectedImages()
 {
   return m_SelectedImages;
 }
 
 void mitk::LevelWindowManager::RecalculateLevelWindowForSelectedComponent(const itk::EventObject &event)
 {
   DataStorage::SetOfObjects::ConstPointer all = this->GetRelevantNodes();
   for (DataStorage::SetOfObjects::ConstIterator it = all->Begin(); it != all->End(); ++it)
   {
     DataNode::Pointer node = it->Value();
     if (node.IsNull())
       continue;
 
     bool isSelected = false;
     node->GetBoolProperty("selected", isSelected);
     if (isSelected)
     {
       LevelWindow selectedLevelWindow;
       node->GetLevelWindow(selectedLevelWindow); // node is an image node because of predicates
 
       auto *image = dynamic_cast<Image *>(node->GetData());
       int displayedComponent = 0;
       if (image && (node->GetIntProperty("Image.Displayed Component", displayedComponent)))
       { // we found a selected image with a displayed component
         // let's recalculate the levelwindow for this.
         selectedLevelWindow.SetAuto(image, true, true, static_cast<unsigned>(displayedComponent));
         node->SetLevelWindow(selectedLevelWindow);
       }
     }
 
     LevelWindow levelWindow;
     node->GetLevelWindow(levelWindow);
   }
 
   this->Update(event);
 }
 
 void mitk::LevelWindowManager::Update(const itk::EventObject &)
 {
   if (m_LevelWindowMutex) // no mutex, should still help
   {
     return;
   }
 
   if (m_AutoTopMost)
   {
     SetAutoTopMostImage(true);
     return;
   }
 
   if (m_SelectedImages)
   {
     SetSelectedImages(true);
     return;
   }
 
   int maxVisibleLayer = itk::NumericTraits<int>::min();
-  DataNode::Pointer highestVisible = nullptr;
-  std::vector<DataNode::Pointer> visProbNodes;
+  DataNode::Pointer topLevelNode = nullptr;
+  std::vector<DataNode::Pointer> nodesForLevelWindow;
 
   DataStorage::SetOfObjects::ConstPointer all = this->GetRelevantNodes();
   for (DataStorage::SetOfObjects::ConstIterator it = all->Begin(); it != all->End(); ++it)
   {
     DataNode::Pointer node = it->Value();
 
     if (node.IsNull())
     {
       continue;
     }
 
-    bool visible = node->IsVisible(nullptr);
-    if (visible)
+    if (node->IsVisible(nullptr) == false)
     {
-      int layer = -1;
-      node->GetIntProperty("layer", layer);
-      if (layer > maxVisibleLayer)
-      {
-        maxVisibleLayer = layer;
-        highestVisible = node;
-      }
+      continue;
+    }
 
-      bool prop = false;
-      node->GetBoolProperty("imageForLevelWindow", prop);
-      if (prop)
-      {
-        visProbNodes.push_back(node);
-      }
+    bool prop = false;
+    node->GetBoolProperty("imageForLevelWindow", prop);
+    if (prop)
+    {
+      nodesForLevelWindow.push_back(node);
+      continue;
+    }
+
+    int layer = -1;
+    node->GetIntProperty("layer", layer);
+    if (layer > maxVisibleLayer)
+    {
+      // top level node is backup node, if no node with
+      // "imageForLevelWindow" property with value "true" is found
+      topLevelNode = node;
+      maxVisibleLayer = layer;
     }
   }
 
-  int numVisProbNodes = visProbNodes.size();
-  if (numVisProbNodes > 2)
+  int nodesForLevelWindowSize = nodesForLevelWindow.size();
+  if (nodesForLevelWindowSize > 2)
   {
     MITK_ERROR << "Error: not more than two visible nodes are expected to have the imageForLevelWindow property set at "
                   "any point.";
   }
-  else if (numVisProbNodes == 2)
+
+  if (nodesForLevelWindowSize > 0)
   {
-    for (std::vector<DataNode::Pointer>::const_iterator it = visProbNodes.begin(); it != visProbNodes.end(); ++it)
+    // 1 or 2 nodes for level window found
+    for (std::vector<DataNode::Pointer>::const_iterator it = nodesForLevelWindow.begin(); it != nodesForLevelWindow.end(); ++it)
     {
-      LevelWindowProperty::Pointer newProp =
-        dynamic_cast<LevelWindowProperty *>((*it)->GetProperty("levelwindow"));
+      LevelWindowProperty::Pointer newProp = dynamic_cast<LevelWindowProperty *>((*it)->GetProperty("levelwindow"));
       if (newProp != m_LevelWindowProperty)
       {
-        this->SetLevelWindowProperty(newProp);
+        SetLevelWindowProperty(newProp);
         return;
       }
     }
   }
-  else if (numVisProbNodes == 1)
-  {
-    LevelWindowProperty::Pointer newProp =
-      dynamic_cast<LevelWindowProperty *>(visProbNodes[0]->GetProperty("levelwindow"));
-    if (newProp != m_LevelWindowProperty)
-    {
-      this->SetLevelWindowProperty(newProp);
-      return;
-    }
-  }
-  else if (highestVisible)
+  else if (topLevelNode)
   {
+    // no nodes for level window found
     LevelWindowProperty::Pointer lvlProp =
-      dynamic_cast<LevelWindowProperty *>(highestVisible->GetProperty("levelwindow"));
-
-    this->SetLevelWindowProperty(lvlProp);
+      dynamic_cast<LevelWindowProperty *>(topLevelNode->GetProperty("levelwindow"));
+    SetLevelWindowProperty(lvlProp);
   }
   else
   {
+    // no nodes for level window found and no visible top level node found
     Modified();
   }
 }
 
 void mitk::LevelWindowManager::UpdateSelected(const itk::EventObject &)
 {
   if (m_LevelWindowMutex) // no mutex, should still help
   {
     return;
   }
 
   if (m_SelectedImages)
   {
     SetSelectedImages(true);
   }
 }
 
 mitk::DataStorage::SetOfObjects::ConstPointer mitk::LevelWindowManager::GetRelevantNodes()
 {
   if (m_DataStorage.IsNull())
-    return DataStorage::SetOfObjects::ConstPointer(DataStorage::SetOfObjects::New()); // return empty set
+  {
+    return DataStorage::SetOfObjects::ConstPointer(DataStorage::SetOfObjects::New());
+  }
 
   NodePredicateProperty::Pointer notBinary = NodePredicateProperty::New("binary", BoolProperty::New(false));
   NodePredicateProperty::Pointer hasLevelWindow = NodePredicateProperty::New("levelwindow", nullptr);
 
   NodePredicateDataType::Pointer isImage = NodePredicateDataType::New("Image");
   NodePredicateDataType::Pointer isDImage = NodePredicateDataType::New("DiffusionImage");
   NodePredicateDataType::Pointer isTImage = NodePredicateDataType::New("TensorImage");
   NodePredicateDataType::Pointer isOdfImage = NodePredicateDataType::New("OdfImage");
   NodePredicateDataType::Pointer isShImage = NodePredicateDataType::New("ShImage");
   NodePredicateOr::Pointer predicateTypes = NodePredicateOr::New();
   predicateTypes->AddPredicate(isImage);
   predicateTypes->AddPredicate(isDImage);
   predicateTypes->AddPredicate(isTImage);
   predicateTypes->AddPredicate(isOdfImage);
   predicateTypes->AddPredicate(isShImage);
 
   NodePredicateAnd::Pointer predicate = NodePredicateAnd::New();
   predicate->AddPredicate(notBinary);
   predicate->AddPredicate(hasLevelWindow);
   predicate->AddPredicate(predicateTypes);
 
   DataStorage::SetOfObjects::ConstPointer relevantNodes = m_DataStorage->GetSubset(predicate);
 
   return relevantNodes;
 }
 
 mitk::Image *mitk::LevelWindowManager::GetCurrentImage()
 {
   return m_CurrentImage;
 }
 
 void mitk::LevelWindowManager::ClearPropObserverLists()
 {
   for (auto iter = m_ObserverToVisibleProperty.begin(); iter != m_ObserverToVisibleProperty.end(); ++iter)
   {
     (*iter).second->RemoveObserver((*iter).first.first);
     (*iter).second = nullptr;
   }
   m_ObserverToVisibleProperty.clear();
 
   for (auto iter = m_ObserverToLayerProperty.begin(); iter != m_ObserverToLayerProperty.end(); ++iter)
   {
     (*iter).second->RemoveObserver((*iter).first.first);
     (*iter).second = nullptr;
   }
   m_ObserverToLayerProperty.clear();
 
   for (auto iter = m_ObserverToRenderingModeProperty.begin(); iter != m_ObserverToRenderingModeProperty.end(); ++iter)
   {
     (*iter).second->RemoveObserver((*iter).first.first);
     (*iter).second = nullptr;
   }
   m_ObserverToRenderingModeProperty.clear();
 
   for (auto iter = m_ObserverToDisplayedComponentProperty.begin(); iter != m_ObserverToDisplayedComponentProperty.end(); ++iter)
   {
     (*iter).second->RemoveObserver((*iter).first.first);
     (*iter).second = nullptr;
   }
   m_ObserverToDisplayedComponentProperty.clear();
 
   for (auto iter = m_ObserverToLevelWindowImageProperty.begin(); iter != m_ObserverToLevelWindowImageProperty.end(); ++iter)
   {
     (*iter).second->RemoveObserver((*iter).first.first);
     (*iter).second = nullptr;
   }
   m_ObserverToLevelWindowImageProperty.clear();
 
   for (auto iter = m_ObserverToSelectedProperty.begin(); iter != m_ObserverToSelectedProperty.end(); ++iter)
   {
     (*iter).second->RemoveObserver((*iter).first.first);
     (*iter).second = nullptr;
   }
   m_ObserverToSelectedProperty.clear();
 }
 
 void mitk::LevelWindowManager::CreatePropObserverLists()
 {
   if (m_DataStorage.IsNull()) // check if data storage is set
   {
     itkExceptionMacro("DataStorage not set");
   }
 
   /* add observers for all relevant nodes */
   DataStorage::SetOfObjects::ConstPointer all = this->GetRelevantNodes();
   for (DataStorage::SetOfObjects::ConstIterator it = all->Begin(); it != all->End(); ++it)
   {
     if ((it->Value().IsNull()) || (it->Value() == m_NodeMarkedToDelete))
     {
       continue;
     }
 
     /* register listener for changes in visible property */
     itk::ReceptorMemberCommand<LevelWindowManager>::Pointer command =
       itk::ReceptorMemberCommand<LevelWindowManager>::New();
     command->SetCallbackFunction(this, &LevelWindowManager::Update);
     unsigned long visIdx = it->Value()->GetProperty("visible")->AddObserver(itk::ModifiedEvent(), command);
     m_ObserverToVisibleProperty[PropDataPair(visIdx, it->Value())] = it->Value()->GetProperty("visible");
 
     /* register listener for changes in layer property */
     itk::ReceptorMemberCommand<LevelWindowManager>::Pointer command2 =
       itk::ReceptorMemberCommand<LevelWindowManager>::New();
     command2->SetCallbackFunction(this, &LevelWindowManager::Update);
     unsigned long layerIdx = it->Value()->GetProperty("layer")->AddObserver(itk::ModifiedEvent(), command2);
     m_ObserverToLayerProperty[PropDataPair(layerIdx, it->Value())] = it->Value()->GetProperty("layer");
 
     /* register listener for changes in layer property */
     itk::ReceptorMemberCommand<LevelWindowManager>::Pointer command3 =
       itk::ReceptorMemberCommand<LevelWindowManager>::New();
     command3->SetCallbackFunction(this, &LevelWindowManager::Update);
     BaseProperty::Pointer imageRenderingMode = it->Value()->GetProperty("Image Rendering.Mode");
     if (imageRenderingMode.IsNotNull())
     {
       unsigned long rendIdx = imageRenderingMode->AddObserver(itk::ModifiedEvent(), command3);
       m_ObserverToRenderingModeProperty[PropDataPair(rendIdx, it->Value())] = imageRenderingMode.GetPointer();
     }
 
     itk::ReceptorMemberCommand<LevelWindowManager>::Pointer command4 =
       itk::ReceptorMemberCommand<LevelWindowManager>::New();
     command4->SetCallbackFunction(this, &LevelWindowManager::RecalculateLevelWindowForSelectedComponent);
     BaseProperty::Pointer displayedImageComponent = it->Value()->GetProperty("Image.Displayed Component");
     if (displayedImageComponent.IsNotNull())
     {
       unsigned long dispIdx = displayedImageComponent->AddObserver(itk::ModifiedEvent(), command4);
       m_ObserverToDisplayedComponentProperty[PropDataPair(dispIdx, it->Value())] = displayedImageComponent.GetPointer();
     }
 
     itk::ReceptorMemberCommand<LevelWindowManager>::Pointer command5 =
       itk::ReceptorMemberCommand<LevelWindowManager>::New();
     command5->SetCallbackFunction(this, &LevelWindowManager::Update);
     BaseProperty::Pointer imgForLvlWin = it->Value()->GetProperty("imageForLevelWindow");
     if (imgForLvlWin.IsNull())
     {
       it->Value()->SetBoolProperty("imageForLevelWindow", false);
       imgForLvlWin = it->Value()->GetProperty("imageForLevelWindow");
     }
     unsigned long lvlWinIdx = imgForLvlWin->AddObserver(itk::ModifiedEvent(), command5);
     m_ObserverToLevelWindowImageProperty[PropDataPair(lvlWinIdx, it->Value())] = it->Value()->GetProperty("imageForLevelWindow");
 
     itk::ReceptorMemberCommand<LevelWindowManager>::Pointer command6 =
       itk::ReceptorMemberCommand<LevelWindowManager>::New();
     command6->SetCallbackFunction(this, &LevelWindowManager::UpdateSelected);
     BaseProperty::Pointer selectedDataNode = it->Value()->GetProperty("selected");
     if (selectedDataNode.IsNull())
     {
       it->Value()->SetBoolProperty("selected", false);
       selectedDataNode = it->Value()->GetProperty("selected");
     }
     unsigned long selectedIdx = selectedDataNode->AddObserver(itk::ModifiedEvent(), command5);
     m_ObserverToSelectedProperty[PropDataPair(selectedIdx, it->Value())] = it->Value()->GetProperty("selected");
   }
 }