Has anyone had shots compromised by the front curtain electronic shutter? I read up on the front curtain shutter here: Electronic Front Curtain Shutters and the theoretical downside that if you use a high shutter speed with a lens full open (i.e. a lot of light coming in that needs to read out REALLY quickly) that ghosting can occur. Has anyone actually experienced this, to the point where you had to switch back to mechanical first shutter??