I have a question about my Olympus PEN E-P2 (and VF-2). Why is the aperture fixed to f/2.8 when using the viewfinder or the live view display, even when the lens goes down to f/1.7? In low-light situations this result in a very noisy viewfinder image. This can be resolved by holding the depth-of-field preview button, which sets the aperture to f/1.7 until you let the button go. Is there a way to have the depth-of-field preview on permanently?