Beware: there is a huge
myth on this, so I understand that you don`t understand this. I don`t understand it, too
Think that when shooting handheld, the movement induced by arms (vibration) is waaaay higher (<<much higher>>) than the one from the mirror slap, so the mirror is not an issue at all. It looks like some can hold a camera like screwed over concrete, up to the point that the mirror vibrations cause unsharpness while their body don`t... (!)
Camera shake is caused by an angular movement; a lighter camera is not necessarily better to avoid this movement. In fact, I`d say the opposite, as a bigger mass need a higher force to be moved. Hmmm, and what about
ergonomics? I think it plays a more important role here, even more than a lighter or heavier weight. And...
Just one more thing;
"still maintain a sharp image". What does it mean? It`s obvious that handholding a camera will cause image unsharpness. So, is there a point where an unsharp image is sharp? Is there somebody that when shooting handheld, get the very same level of sharpness/unsharpness on each shot? I think not.