I'm sure there is a discussion line out there, but I couldn't find it.
Quick question: Is it necessary to focus modern zoom lenses at longest focal length first, then recompose to shoot? or Can you rely on autofocus to work accurately at any focal length?
no focus at the length you want. Most if not all zooms are not parafocal (probably as with AF they dont really need to be) so will change focus with zoom.
