Image control loaded tif file without quality DPI

Question

As i load the tif file in image control ,the tif files shown blur,how to improve the quality(DPI) of tif file

source code:

private void RibbonButton_Click(object sender, RoutedEventArgs e)

{

   Microsoft.Win32.OpenFileDialog dlg = new Microsoft.Win32.OpenFileDialog();

   dlg.InitialDirectory = "c:\\";

   dlg.Filter = "Image files (*.tif)|*.tif|All Files (*.*)|*.*";

   dlg.RestoreDirectory = true;

   bool? result = dlg.ShowDialog();

   {

      string selectedFileName = dlg.FileName;

      FileNameLabel.Content = selectedFileName;

      BitmapImage bitmap = new BitmapImage();

      bitmap.BeginInit();

      bitmap.UriSource = new Uri(selectedFileName);

      bitmap.EndInit();

      ImageViewer1.Source = bitmap;

      }

}