i have a pro camera, mark 3 5d. i have the kit lens 70mm-105mm 4.0 aperture and i switch the lens to auto focus. i also hold AF-on while viewing viewfinder along with shutter press. but my eyes are not viewing the focus. i have tried to set the diopter control to see but i dont think its that. I take a pic and most of the time it comes blurry. it is especially blurry when i tried to zoom in and even if i adjust the focus ring nothing comes out of it. i would think its the low light situation in my room as i only have a lamp and a 120d aputure lighting set. Can anyone explain?