[m42man]

Adam said it before, but just to expand (if I may), the main situations which benefit from MF are:

1. When it's important to have a good DOF which extends to infinity: landscapes fit the bill here, and you'd be talking about hyperfocal focusing, which doesn't involve use of the AF mechanism (or the human eye either).

2. When the AF system doesn't know what object (or part of object) to focus on: this may be when the DOF is so thin only part of the subject can be in focus (when the lens is wide open), i.e. macro photography; or it may be just that the subject is encroached by other objects which aren't in the same plane as the subject - i.e. when the scene is very cluttered.

3. When the AF system just plain doesn't work - as in a low-light situation.

In most (all?) other situations, AF is a delightful attribute to have - I sincerely wish all my MF lens were AF. And I seem to be lucky, in that I've never had any issues with front/back focus using my K-m.

[Marc Sabatella]

That's a different question, though. Sure, there are many times when I might prefer using MF, but I can do that with an AF lens, too. The focus rings on an MF lens is usually nicer, though,