I have been meaning to ask this for a while now. As i'm progressing into learning more and more about the wonderful world of photography, I am starting to find that I need to use manual focus more than relying so heavily on auto focus. My question is, how do you know if you're focused or not in MF? I can obviously adjust the focusing ring all that I want, and make it so that it looks focused through the viewfinder, but i've often been finding that when I get back onto the computer and view the pictures in full screen, they appear to be slightly off-focus almost every time. Is there a sure-fire way to use MF and know that you're going to get a crisp, clean exposure? Or is the success of your exposure when using MF heavily dependent on your aperture choice?