diff --git a/EXE_Scene.cpp b/EXE_Scene.cpp
index 259b23a..be755fc 100644
--- a/EXE_Scene.cpp
+++ b/EXE_Scene.cpp
@@ -1008,7 +1008,7 @@ CALLBACK SceneBoxProc( HWND hwndDlg, UINT message, WPARAM wParam, LPARAM lParam)
    case WM_INITDIALOG :
       {
         // imposto dimensione box e picture
-         const int WIN_MAX_DIM = 1024 ;
+         const int WIN_MAX_DIM = ( s_nDriver == 1 ? 512 : 1024) ;
          int nWinW = ( s_nWidth >= s_nHeight ? WIN_MAX_DIM : ( WIN_MAX_DIM * s_nWidth) / s_nHeight) ;
          int nWinH = ( s_nHeight >= s_nWidth ? WIN_MAX_DIM : ( WIN_MAX_DIM * s_nHeight) / s_nWidth) ;
          HWND hPic = GetDlgItem( hwndDlg, IDC_PICTURE1) ;
@@ -1023,10 +1023,15 @@ CALLBACK SceneBoxProc( HWND hwndDlg, UINT message, WPARAM wParam, LPARAM lParam)
                s_nContext = nContext ;
                pGseCtx->m_pScene->SetCamera( s_nCameraDir) ;
                pGseCtx->m_pScene->ZoomAll() ;
-               pGseCtx->m_pScene->GetImage( s_nShowMode, s_colBackTop, s_colBackBottom, s_nWidth, s_nHeight, s_sImageFile) ;
+               if ( ! pGseCtx->m_pScene->GetImage( s_nShowMode, s_colBackTop, s_colBackBottom, s_nWidth, s_nHeight, s_sImageFile))
+                  s_nContext = -s_nContext ;
                MyResetGroupObjGraphics( pGseCtx->m_pGeomDB, GDB_ID_ROOT) ;
                EndDialog( hwndDlg, wParam) ; 
             }
+            else {
+               s_nContext = 0 ;
+               EndDialog( hwndDlg, wParam) ; 
+            }
          }
          else
             s_nContext = 0 ;
@@ -1063,9 +1068,9 @@ ExeGetImageEx( int nDriver, bool b2Buff, int nColorBits, int nDepthBits,
      // lancio dialogo
       HWND hTopWnd = ExeGetMainWindowHandle() ;
       DialogBox( GetModuleIstance(), MAKEINTRESOURCE( IDD_LUASCENE), hTopWnd, (DLGPROC)SceneBoxProc) ;
-      bool bOk = ( s_nContext != 0) ;
+      bool bOk = ( s_nContext > 0) ;
      // elimino la scena dal contesto
-      GseContext* pGseCtx = GetGseContext( s_nContext) ;
+      GseContext* pGseCtx = GetGseContext( abs( s_nContext)) ;
       if ( pGseCtx != nullptr) {
          delete pGseCtx->m_pScene ;
          pGseCtx->m_pScene = nullptr ;