On my Canon 7 at slower shutter speeds I hear an weird "after-sound" -- the click doesn't end cleanly but there's a faint "tick - tick - tick " after the release. I certainly notice it at 1/30 or slower, maybe at 1/60th, but from 1/125 and faster it's not there. Almost like something is bouncing along till it stops. Any ideas on what this might be, and whether it's a worry. Pictures seem to come out fine!