I just picked up a E-M1 at my local camera shop. I notice that when I half depress the shutter button to focus, I hear a hissing-like noise which sounds something like a motor running. It continues until a moment or so after completely depressing the button and taking the picture. I never really noticed this noise with my EM-5. I hear it regardless of which of my lenses I use. Is this a normal sound? Any help would be appreciated. Thanks.