The 14-45 I recently acquired causes a weird shutter sound on my EM5. All other lens(legacy included) have the same snappy actuation sound. This one, however, has a slow "k-chunk" sound and feel, like a long exposure. I noticed it when comparing it to a 12-35. I've shot 1/1000 exposure( aperture priority) with same sound. The images are sharp .Autofocus is quick and accurate. Does the aperture change at the moment of actuation or when set? Sticky aperture? Is anyone familiar with this phenomenon? I'd appreciate any advice or opinion.