Thanks , while being cognizant of confirmation bias I think this answers my question . Was hoping there was another trick I was missing . It ' s just tough when you ' re wide open and the micro focus is the difference between the eye or the eye brow . For what it ' s worth , here ' s what I ' ve discovered from testing different focusing methods , ranked from least accurate to most accurate . 1 Least accurate manual focusing until the green dot appears in the corner of the screen . There ' s a tolerance to what the AF sensor considers in focus . Try pulling and pushing focus , you ' ll notice the green dot stays on even when you move the focus ring . This happens to me on the nice Nikon 1970 s ais Nikkor lenses that have long precise buttery focus throws . 2 back button focus the stuttering overachieving micro focusing sometimes might be a little off if you leave your finger on the bbf button or let go of the bbf while it ' s stuttering to fire the shutter applies to stationary objects 3 AF single mode focus priority is a little better than bbf because the AF motor stops micro focusing once focus is achieved . 4 Most accurate LiveView , zoomed in and manual focus .