Assuming this really is a problem, for long exposures use the "hat trick." Hold a card (or hat, thus the name) over the lens while you open the shutter with a release in the other hand. Then let vibrations settle and move the card or hat away from the lens and time the exposure with your watch. Then cover the lens again at the end and then close the shutter. It's harder to describe than to do, plenty accurate for exposures of a few seconds or longer, and cures the problem.
Originally Posted by jovo