diff --git a/openglcanvas.cpp b/openglcanvas.cpp
index 28fe0a19df253459099bcca232294614d738edd3..d61036b8568632ef49fb69d259bd115e24db23c0 100644
--- a/openglcanvas.cpp
+++ b/openglcanvas.cpp
@@ -101,6 +101,7 @@ void OpenGLCanvas::change_fov_max(int new_fov_max){
             scale=log(exp(1.f)+(1.f-exp(1.f))*(fov-fov_max)/(360.-2*fov_max));
     }
     fprintf(stderr,"change fov_max=%f, new scale=%f\n",fov_max,scale);
+    emit max_fov_changed((int)fov_max);
     updateGL();
 }
 
@@ -674,7 +675,11 @@ void OpenGLCanvas::mouseMoveEvent(QMouseEvent *event){
 
 void OpenGLCanvas::wheelEvent(QWheelEvent *event){
     if(event->orientation()==Qt::Vertical){
-        change_fov(fov+((double)event->delta())/60);
+        if(event->modifiers()==Qt::ControlModifier){
+            change_fov_max(fov_max+((double)event->delta())/30);
+        }else{
+            change_fov(fov+((double)event->delta())/30);
+        }
     }
 }
 
@@ -725,7 +730,7 @@ void OpenGLCanvas::paintGL(){
             time_fps = time_frames/dt;
             time_frames = 0;
             time_time.reset();
-            emit fps(QString("%1 fps").arg((int)(time_fps+0.5)));
+            //emit fps(QString("%1 fps").arg((int)(time_fps+0.5)));
             printf("fps = %d ", (int)(time_fps+0.5));
 //        }
 //    }
diff --git a/openglcanvas.h b/openglcanvas.h
index 388298abcacec620a92c6d3c4231ac80198b8e6a..2ca440fccaccb34dd49d9acb1b5ea7bf632c794a 100644
--- a/openglcanvas.h
+++ b/openglcanvas.h
@@ -62,6 +62,7 @@ protected:
 signals:
     void fps(QString newFPS);
     void fov_changed(int new_fov);
+    void max_fov_changed(int new_max_fov);
 
 public slots:
     void change_fov(double f);
diff --git a/panowindow1.ui b/panowindow1.ui
index 018716d9bd96b695d1ce7c3dd67740bb77a18764..9f8ba6ea5adbe588011bdc74e7a4bb068a06d94f 100644
--- a/panowindow1.ui
+++ b/panowindow1.ui
@@ -157,10 +157,10 @@
    <item row="10" column="1" alignment="Qt::AlignHCenter">
     <widget class="QSlider" name="changefovmax">
      <property name="minimum">
-      <number>10</number>
+      <number>1</number>
      </property>
      <property name="maximum">
-      <number>180</number>
+      <number>359</number>
      </property>
      <property name="sliderPosition">
       <number>60</number>
@@ -187,6 +187,7 @@
    <container>1</container>
    <slots>
     <signal>fov_changed(int)</signal>
+    <signal>max_fov_changed(int)</signal>
     <slot>change_fov(double)</slot>
     <slot>change_scale(double)</slot>
     <slot>change_center_lambda(double)</slot>
@@ -330,5 +331,21 @@
     </hint>
    </hints>
   </connection>
+  <connection>
+   <sender>GLCanvas</sender>
+   <signal>max_fov_changed(int)</signal>
+   <receiver>changefovmax</receiver>
+   <slot>setValue(int)</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>250</x>
+     <y>249</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>532</x>
+     <y>262</y>
+    </hint>
+   </hints>
+  </connection>
  </connections>
 </ui>