So, ideally I'd like to keep the aperture wide precisely because I want the low depth-of-field. As it happens my lens isn't a very fast one (55–200 mm f/4.0–5.6), and a fair few of my photos were stopped down to around f/6–8 anyway, especially the ones where I had switched to manual, but the reason I was asking for assistance on how to nail the focus is to help get the sharpest subject I can and be able to keep a nice soft background.