Re: Help me understand focusing on viewfinder camera
Tom,
A few thoughts, starting with your comment on post #9 that all the issues with manually focusing a SLR are still there with a rangefinder...
The process is actually quite different on a rangefinder, and quite a bit easier than manually focusing on an SLR. For example, you don't have to open up the lens to focus on a rangefinder, since your view is not TTL (through the lens). It tends to be a faster and more accurate process on the rangefinder.
As for your last question, regarding DOF...
Just like an SLR, accurate focus is more critical when shooting a long lens and/or wide aperture.
If the subject is fairly still, it's not a problem on a rangefinder, as you can put the "patch" directly over the important part (i.e. eyes of the subject), and then precisely focus the lens.
The of the rangefinder "patch" as the equivalent of the single center AF point, but with the ability to be actually more precise than an a typical AF system.
I have a lot of trouble focusing a 50/1.4, 75/2, 75/1.4, 90/2 at wide open apertures if the subject is moving around quickly. In those cases, a good AF system (i.e. Canon 1-series) is far superior to get a high percentage of keepers.
That's one reason why I still keep a DSLR, even though the M9 is my main system. When I'm going to shoot sports, kids playing the surf, birds flying, etc., I grab my 7D with a telephoto lens, and rely on the AF system.
For everything else, I far prefer the M9.
Rangefinder-coupled lenses are well designed for manually focusing. They have a nice amount of "throw" (amount of rotation of the focus ring from near focus to infinity) that allows you to quickly cover the entire range, while also making very accurate small increments when you are fine-tuning your focus. They work quite differently this way than a typical SLR AF lens.
If you decide to try a rangefinder camera, you might start with an M8 and just an inexpensive lens or two, to see how you like it. Give yourself some time to get used to it. You won't be effective with the camera in the first day or two, so don't make a premature conclusion. Allow yourself a few weeks with the camera in non-critical shooting situations to develop a feel for how they work, and how to quickly achieve accurate focus. Then try it out in more demanding situations, and then you can decide if the system works for you.
Be sure to keep a DSLR system around too, as you'll definitely need it for certain situations.
Hope this helps,
Mike