The fundamental undoing of the Olympus OM system camera bodies are not mirror slap (yes, it's mostly true the rangefinder vs. slr had-holdability is an old wives' tale - few SLR mirrors have enough inertia to cause visible vibration in the hands of a human being, which have a lot more inertia than a tiny mirror) - but rather the aperture stop-down mechanism.
Unlike, say, Nikon F, where the body merely has to gently prod the aperture to stop down, which does so under the power of its own spring, an OM body provides the full force for the stop-down. The body has to slam aperture lever with all it's got, in order to be able to move giant aperture stop-down mechanisms of lenses like the 250mm f/2.0 or 1000mm f/11.
The aforementioned Gary Reese lens tests illustrates the disastrous effect this has on image quality taken with certain lenses on tripod - regardless of mirror lockup.
The effect is substantial, and often makes OM cameras much better hand-held (with "wet" vibration absorption by a human being) than on a tripod. I use a giant top-of-the-line Gitzo Tele Studex Carbon Fibre tripod (which easily holds my 4x5in large format camera and 500mm lens rock solid - 6kg or so), yet many tripod-mounted shots with my OM 250mm f/2.0 are blurred by camera shake.
On the other hand, I can hand-hold either this lens, or any other smaller one, on an OM body with surprisingly slow shutter speeds and get shake-free results. For example, this was hand-held at 1/4s:
(OM-2n, 24mm at f/2.0, 8x10 darkroom hand print)
An odd (but lovely, nevertheless!) system, the OM system.
Here's a chance to put some internet noise to rest:
What's the truth about mirror slap effectively canceling out a stop of a lens' capability?
I've heard and read that old chestnut many times, and assume it means vibrations triggered by the mirror preclude hand holding SLR's when the lens is wide open.
But my Oly seems as steady as any camera I've used. Has anyone found they cannot reliably use Zuiko lenses wide open and hand held on an OM body because of mirror slap?