It’s often human nature for people to blame the equipment instead of chalking it up to operator error, LOL! Especially when at a beginner or novice level, before the knowledge of the focusing system / process really gets embedded. First thing, if you understand the focusing system and how it works, you can test your equipment to eliminate that as the culprit. Get a hold of a focus test chart online and test it that way…..try it with all your lenses and note results or variances. Now then, here are the factors that usually cause out of focus images, back focusing, etc.
- Too slow of a shutter speed….whether shooting on an auto mode of sorts and the camera selects too low of a shutter speed, or you select it yourself. This is one reason I like manual mode. Control. Most people can hand hold 1/30 sec to 1/125 sec…..even many seasoned pros cannot go slower than that without a tripod or monopod. I have had a mixed result with 1/30 personally with a still subject…..depends on how long of a lens, my own level of fatigue, and the motion of the subject. Camera shake comes from the photographer…..but blur can come from that or the subject moving too fast for that shutter speed. It’s one thing if motion blue is the premise of the photo….but when it looks accidental it’s not a good thing, or a successful attempt at impressionism. For standard portraiture, I usually use 1/160 of a sec or faster to be safe….also depending are whether strobes or flash guns are used, shutter sync speed will have a limit of 1/200 or 1/250 in most cases.
-Also improper use of auto focus. Usually when the focus ends up sharp on the wrong part of the photo….it’s from not selecting the focus point properly. In standard AF mode, the camera searches for the nearest object and usually locks focus on it. If it locks it in the right spot….follow the red dots, you’ll know if you take the time to pay attention rather than shoot 189 miles a second LOL! You can achieve the best bokeh this way if shooting shallow depth of field. I usually use a center point focus, making one focus point that you adjust to fit the focal point of your subject. Manual focus is also good to use in some cases…..even then you can have problems if your biopter which is adjustable by turning the little knob at your viewfinder, is out of adjustment. It’s the same procedure as adjusting binoculars, when it’s clear it’s in focus….taaaadaaaa! So when this is correct, say you are photographing a wedding party of 2 rows, and you lock your focus point on the bride, in front, between her eyes…..that’s where the sharpest focus should be. If the focus is on someone in the back, that’s backfocusing. Whether you moved after locking your focus point or there is a fault with the lens or body. Unlikely it’s the latter.
-I’ll close with this….also moving after you lock your focus point, or the subject moving after you lock your focus point will cause the focus to land on the wrong part of the image. For moving subjects, panning or AI servo is a better choice than one shot focus. All things to consider if having consistent issues. Always backtrack and think about your steps before blaming equipment and giving vendors your money.