diff --git a/Modules/OpenCVVideoSupport/Commands/mitkConvertGrayscaleOpenCVImageFilter.cpp b/Modules/OpenCVVideoSupport/Commands/mitkConvertGrayscaleOpenCVImageFilter.cpp
index fc70d7685c..3e73885fe1 100644
--- a/Modules/OpenCVVideoSupport/Commands/mitkConvertGrayscaleOpenCVImageFilter.cpp
+++ b/Modules/OpenCVVideoSupport/Commands/mitkConvertGrayscaleOpenCVImageFilter.cpp
@@ -1,34 +1,36 @@
 /*===================================================================
 
 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 "mitkConvertGrayscaleOpenCVImageFilter.h"
 
 #include "cv.h"
 
 namespace mitk {
 
 bool ConvertGrayscaleOpenCVImageFilter::FilterImage( cv::Mat& image )
 {
   cv::Mat buffer;
 
   cv::cvtColor(image, buffer, CV_RGB2GRAY, 1);
+
+  // content of buffer should now be the conten of image
   image.release();
   image = buffer;
 
   return true;
 }
 
 } // namespace mitk
diff --git a/Modules/OpenCVVideoSupport/Commands/mitkCropOpenCVImageFilter.cpp b/Modules/OpenCVVideoSupport/Commands/mitkCropOpenCVImageFilter.cpp
index 85c2145e17..0f0aba8f43 100644
--- a/Modules/OpenCVVideoSupport/Commands/mitkCropOpenCVImageFilter.cpp
+++ b/Modules/OpenCVVideoSupport/Commands/mitkCropOpenCVImageFilter.cpp
@@ -1,76 +1,90 @@
 /*===================================================================
 
 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 "mitkCropOpenCVImageFilter.h"
 
 #include "cv.h"
 
 namespace mitk {
 
 bool CropOpenCVImageFilter::FilterImage( cv::Mat& image )
 {
   if (m_CropRegion.width == 0)
   {
     MITK_ERROR("AbstractOpenCVImageFilter")("CropOpenCVImageFilter")
         << "Cropping cannot be done without setting a non-empty crop region first.";
     return false;
   }
 
   cv::Rect cropRegion = m_CropRegion;
 
   // We can try and correct too large boundaries
   if ( cropRegion.x + cropRegion.width >= image.size().width)
   {
     cropRegion.width = image.size().width - cropRegion.x;
+    MITK_WARN("AbstractOpenCVImageFilter")("CropOpenCVImageFilter")
+        << "Changed to large roi in x direction to fit the image size.";
   }
   if ( cropRegion.y + cropRegion.height >= image.size().height)
   {
     cropRegion.height = image.size().height - cropRegion.y;
+    MITK_WARN("AbstractOpenCVImageFilter")("CropOpenCVImageFilter")
+        << "Changed to large roi in y direction to fit the image size.";
   }
 
   cv::Mat buffer = image(cropRegion);
   image.release();
   image = buffer;
 
   return true;
 }
 
 void CropOpenCVImageFilter::SetCropRegion( cv::Rect cropRegion )
 {
   // First, let's do some basic checks to make sure rectangle is inside of actual image
-  if (cropRegion.x < 0) { cropRegion.x = 0; }
-  if (cropRegion.y < 0) { cropRegion.y = 0; }
+  if (cropRegion.x < 0)
+  {
+    MITK_WARN("AbstractOpenCVImageFilter")("CropOpenCVImageFilter")
+        << "Changed negative x value in roi to 0.";
+    cropRegion.x = 0;
+  }
+  if (cropRegion.y < 0)
+  {
+    cropRegion.y = 0;
+    MITK_WARN("AbstractOpenCVImageFilter")("CropOpenCVImageFilter")
+        << "Changed negative y value in roi to 0.";
+  }
 
   // Nothing to save, throw an exception
   if ( cropRegion.height < 0 || cropRegion.width < 0 )
   {
     mitkThrow() << "Invalid boundaries supplied to USImageVideoSource::SetRegionOfInterest()";
   }
 
   m_CropRegion = cropRegion;
 }
 
 void CropOpenCVImageFilter::SetCropRegion( int topLeftX, int topLeftY, int bottomRightX, int bottomRightY )
 {
   this->SetCropRegion( cv::Rect(topLeftX, topLeftY, bottomRightX - topLeftX, bottomRightY - topLeftY) );
 }
 
 cv::Rect CropOpenCVImageFilter::GetCropRegion( )
 {
   return m_CropRegion;
 }
 
 } // namespace mitk
diff --git a/Modules/OpenCVVideoSupport/Commands/mitkCropOpenCVImageFilter.h b/Modules/OpenCVVideoSupport/Commands/mitkCropOpenCVImageFilter.h
index f3eb88ccc5..2f8b9d32ed 100644
--- a/Modules/OpenCVVideoSupport/Commands/mitkCropOpenCVImageFilter.h
+++ b/Modules/OpenCVVideoSupport/Commands/mitkCropOpenCVImageFilter.h
@@ -1,55 +1,66 @@
 /*===================================================================
 
 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.
 
 ===================================================================*/
 
 #ifndef mitkAbstractOpenCVImageFilter_h
 #define mitkAbstractOpenCVImageFilter_h
 
 #include "mitkAbstractOpenCVImageFilter.h"
 
 #include "cv.h"
 
 //itk headers
 #include <itkObjectFactory.h>
 
 namespace mitk {
 
 class MITK_OPENCVVIDEOSUPPORT_EXPORT CropOpenCVImageFilter : public AbstractOpenCVImageFilter
 {
 
 public:
   mitkClassMacro(CropOpenCVImageFilter, AbstractOpenCVImageFilter);
   itkNewMacro(Self);
 
   /**
     * \brief Crops image to rectangle given by mitk::CropOpenCVImageFilter::SetCropRegion.
     * \return false if no crop region was set or the crop region width is zero, true otherwise.
     */
   bool FilterImage( cv::Mat& image );
 
+  /**
+    * \brief Set region of interest for cropping.
+    */
   void SetCropRegion( cv::Rect cropRegion );
+
+  /**
+    * \brief Set region of interest for cropping.
+    */
   void SetCropRegion( int topLeftX, int topLeftY, int bottomRightX, int bottomRightY );
+
+  /**
+    * \brief Returns region, which was set by mitk::CropOpenCVImageFilter::SetCropRegion().
+    */
   cv::Rect GetCropRegion( );
 
 protected:
   /**
     * \brief Defines the region which will be cropped from the image.
     */
   cv::Rect m_CropRegion;
 };
 
 } // namespace mitk
 
 #endif // mitkAbstractOpenCVImageFilter_h