Something that I've been trying to sort out lately...
Take the following scenario for example. I'm shooting a flower in a bush. I manual-focus on the flower at f/1.8, and take the shot. Now what if I want to get more of the bush in focus, so I step down to f/5.6, but don't touch the manual focus ring. Can I safely assume that the flower is still the focal point / focal distance?
Or the other way around. I start at f/5.6, focus, and then widen aperture to f/1.8. Do I need to re-focus?
Please note that I'm not talking about DOF. I know that DOF changes with aperture size. I'm just referring specifically to the focal point/plane.
In the past, I've been a bit paranoid and recheck the focus and fudged around with the focus ring after changing the aperture to ensure that my original focus subject is still in critically in-focus. But do I need to do this? Theoretically speaking, if my focus (on some object or part of an object) was spot-on initially, I shouldn't need to re-focus after simply changing the aperture right?
Knowing this definitively would help me speed up my work-flow in the field when I'm experimenting with bracketed shots.