About a year ago I attended one of the Leica M9 roadshow workshops and there were a few good tips shared. One of the tips in particular has helped me increase the number of sharp, in focus shots I take, which is always something we're striving to do with rangefinders.
For this tip, think about depth of field and where your focus point lies within the in focus portion of your shot. As you can see in the diagram below, in front of your focus point, you only have 1/3 of your depth of field, whereas behind your focus point you have 2/3 of your depth of field. This is probably old news to many of you, but even after many years of a photography hobby, somehow I had never understood this concept.
So here's where the tip comes....
When focusing, you can approach your focus point from either direction; from the minimum focus distance, or from infinity. Go pull out your M camera and look at the top of the lens with the depth of field markers. You can either rotate it clockwise or counterclockwise to arrive at the point where your subject is in focus.
Now, think about the diagram above. The trick is to always approach the point of focus from the rear, or from infinity, because you're more likely to have the portion of your subject in focus that you desire. If you're a little off, it's probably ok because you've got twice as much depth of field on that side of your focus point.
Give it a try, and feel free to discuss this one. I'm open to hearing if any of you have similar tricks or a variation of this tip to share. Overall I've found that if I approach the focus from infinity rather than hunting back and forth for focus, I have a better chance of of a sharp in-focus subject. Obviously this is critical when shooting the lovely Leica glass wide open!
Diagram credit and more about depth of field: