photoguy6405 wrote in post #6848953
What is "backfocusing"? I see the differences in the pics above, but what is happening to get there?
Backfocusing is a lens or camera condition which causes the DoF-zone (Depth of Field) after AF to start after the actual point where you focused on, IOW, behind the subject you are trying to focus on.
This is what is happening in the above pictures. It was focused at the bar with the "Focus here" text, but focus ended up slightly behind that bar. This is very irritating when shooting nearby subjects, because they tend to be unsharp as a result, or have the sharpness at a different point than where you really want it. Further away this generally is less of a problem, because DoF, which is much more extended further away, then tends to catch these problems. This problem becomes obviosu nearby and with large apertures (small f-numbers); with smaller apertures (higher f-numbers) DoF grows much larger and include the OOF (Out Of Focus) area, provided the problem isn't too big.
However, in many cases this is caused by user error, as one's body always moves a little. This is why you need a good tripod, MLU (Mirror Lock Up) and a remote switch in combination with the focus test chart, or any other good (static) test subject to test whether a lens or camera is back or front focusing. Frontfocus is where after AF the focus falls in front of the subject, towards you.
If a camera front or back focuses, which is very rare, it tends to happen with all your lenses, and not, f.e., with a different camera, while for individual lenses front or back focus will be the same or similar with different bodies. This probably happens with 4 or 5 out of 100 lenses or so.
Kind regards, Wim