it's not the shutter. The shutters in realists are linked mechanically so there's not going to be variation in the exposure between the shutters. However, even though the apertures are liked (by a belt), there IS some slop in those. one aperture will be slightly bigger or smaller depending on which one you rotate to change the size. You can easily clean the realist shutters yourself and tighten the screws if they're coming loose--they are a simple two-leaf shutter in each lens. the screws in the front allow the front plate to come off and voila the internal works.