I recently purchased a Canon 70D for its dual pixel autofocusing system and ISO performance. I am in love with this feature rich-camera; however I found the camera's autofocus fails to function correctly with a 50mm 1.8 prime on manual zone AF mode.
The camera's manual single point AF focuses tack-sharp and quick; similarly the complete auto also lives up to its expectations. However when I set the AF method to manual zone select, it fails to result sharp pictures; the focus points get highlighted and shows to have captured the desired point, but when I preview it on my laptop, I see the focus is slightly under calculated (example: subject at 5ft would be focused around 4.8ft), as I mostly shoot with a lower F number to achieve shallow depth, I often get unusable results.
I am on one-shot mode on AF method. If I switch to manual focus on lens and use the zones for reference, I am able to achieve wonderful results.
I borrowed a 50mm prime from other fellow photographers and the issue still persists. Have I got a bad piece of 70D or is there something I am doing wrong?