This might be a stupid question...but I'm gonna ask anyway. Is there any rule for DOF concerning the distance from the closest point focused on & the in focus area behind this point. For example aT f2.8 will only 1m behing this point be in focus & at say F10 will 12m behind this point still be in focus? Or does this differ from lens to lens. I've never really done any kind of test for this. I understand the concept of DOF but not sure if there are any rules or guidelines.
I need to use manual focus for something & prefocus on a point, but not sure what the best way is to get the best results!