diff --git a/common/dialogs/dialog_image_editor.cpp b/common/dialogs/dialog_image_editor.cpp
index 82bbe23d48..fdd6b180cc 100644
--- a/common/dialogs/dialog_image_editor.cpp
+++ b/common/dialogs/dialog_image_editor.cpp
@@ -29,6 +29,7 @@
 #include <fctsys.h>
 #include <gr_basic.h>
 #include <common.h>
+#include <confirm.h>
 #include <bitmap_base.h>
 
 #include <dialog_image_editor.h>
@@ -119,35 +120,45 @@ void DIALOG_IMAGE_EDITOR::OnHalfSize( wxCommandEvent& event )
 
 /* Test params values correctness
  * Currently scale value must give an actual image
- * > MIN_SIZE pixels and < MAX_SIZE pixels
+ * > MIN_SIZE pixels (mandatory to be able to see the image)
+ * and < MAX_SIZE pixels (if bigger, a confirmation will be asked)
+ * Note: The image definition is 300ppi in drawing routines.
  */
 bool DIALOG_IMAGE_EDITOR::CheckValues()
 {
-    #define MIN_SIZE 16
-    #define MAX_SIZE 6000
+    #define MIN_SIZE 32     // Min size in pixels after scaling
+    #define MAX_SIZE 6000   // Max size in pixels after scaling
     double tmp;
     wxString msg = m_textCtrlScale->GetValue();
 
     // Test number correctness
-    if( ! msg.ToDouble( &tmp ) )
+    if( !msg.ToDouble( &tmp ) || tmp < 0.0 )
     {
         wxMessageBox( _("Incorrect scale number" ) );
         return false;
     }
 
-    // Test value  correctness
+    // Test value correctness
     wxSize psize = m_workingImage->GetSizePixels();
+    int size_min = (int)std::min( (psize.x * tmp), (psize.y * tmp) );
 
-    if( (psize.x * tmp) < MIN_SIZE ||  (psize.y * tmp) < MIN_SIZE )
+    if( size_min < MIN_SIZE )   // if the size is too small, the image will be hard to locate
     {
-        wxMessageBox( _("Scale is too small for this image" ) );
+        wxMessageBox( wxString::Format(
+                   _("This scale gives a too small image size (%.2f mm or %.1f mil)" ),
+                   25.4 / 300 * size_min, 1000.0/300.0 * size_min ) );
         return false;
     }
 
-    if( (psize.x * tmp) > MAX_SIZE ||  (psize.y * tmp) > MAX_SIZE )
+    int size_max = (int)std::max( (psize.x * tmp), (psize.y * tmp) );
+
+    if( size_max > MAX_SIZE )
     {
-        wxMessageBox( _("Scale is too large for this image" ) );
-        return false;
+        // the actual size is 25.4/300 * size_max in mm
+        if( !IsOK( this, wxString::Format(
+                   _("This scale gives a very large image size (%.1f mm or %.2f in). Are you sure?" ),
+                   25.4 / 300 * size_max, size_max /300.0 ) ) )
+            return false;
     }
 
     return true;