I and my new (to me) Mamiya 645 are starting our lives together and are so far quite happy. I've run a roll of TMax 400 film through and was pleased to see good results when I finished developing. It has left me with a few questions though which hopefully the brain trust here can help me sort out.

Firstly, the camera seems only able to shoot in full stops. What do I do when I need to change the exposure by 1/3 of a stop? I'm perfectly happy with full stops on the aperture, but when I shot the roll of film some frames were perfectly exposed, other were too bright or dark by just that little bit. I must be missing some really simple way around this, but shutter speed wheel just locks into speeds one stop apart. Right now I have three print films, two B&W and Ektar 100. I'm nervous about shooting slide film if I won't be able to exactly dial in exposure...

Secondly, I have a modest selection of prime lenses for the camera (35mm, 80mm, 150mm, and 210mm) which I'm reasonably happy with. I suspect the 35mm lens may be too wide to be my only wide-angle lens and am considering adding a 45mm or a 55mm lens. When doing some research I found Mamiya made a 55-110mm lens and that got me thinking. Since my primary plan for this camera is to taking it hiking should I perhaps swap my 80mm and 150mm lens for the 55-110mm lens and kill three birds with one stone? I know I will lose some ability to produce images with a very shallow depth of field but having one lens to replace three is appealing.

All opinions are welcome! I'm heading out in a couple weeks on vacation and I want to be ready!