I've routinely shot my Mamiya 645 at 1/30 or higher without a tripod with good results. Of course, a tripod is an insurance against camera shake but if you have a choice of either no picture (because you don't have a tripod with you) or the shot without one, I'd definitely not pass up a good photo op. Heck, I've even hand held my RB with the 90mm 3.8 with excellent results. It seems that the heavier camera provides a steadier platform.