The Pentax 645 has a dampened mirror to reduce vibration. I have shot it as slow as 1/60th, but my elbows were braced. The Pentax motor has roughly the same noise level as other motor-driven winders I have. Noise level is subjective, though. The widest Pentax 645 lens is 45mm, so that should fit your target lens range. There is a 35mm, but it's a monster fisheye designed for the Pentax 67, and you'll need an adapter to use it on the 645.