I bought this camera mainly for digitizing negatives & slides. It has some issues.
The autofocus isn't sharp through the viewfinder so manual focus is better.
The auto-focus on live view on the rear LCD works fine and is vey sharp and accurate and video mode works fine.
Also, the built in flash or external flash doesn't work.
Despite these issues, I have taken good shots with the live view autofocus and manual focus.
Excellent high ISO and dynamic range performance.
So, autofocus is not sharp through viewfinder but works as it should when in live view LCD screen.
He said AF with viewfinder not sharp not MF as he said he can MF sharp. So it's not the diopter. It has something to do with the AF sensors at the bottom of the mirror box. These sensors only used in viewfinder mode. In liveview the camera uses the imaging sensor for AF. It may have to do with AF fine tuning.