I started out in photography back in the days when there was no such thing as autofocus. If I focused a lens at the wrong distance, it was my fault, pure and simple. Nowadays, most of us rely almost exclusively on autofocus. That’s all well and good if an autofocus system is consistently accurate but, sadly, that’s often not the case. For interchangeable lens cameras, you’re relying on the electronics and mechanics of both the camera and any attached lens to play nicely together and work in complete harmony. They might not.
Autofocus inaccuracy is more of a problem with DSLRs, which have separate autofocus modules and image sensors, in physically different places. That gives more room for error, compared with mirrorless cameras in which autofocus is based on the actual image sensor itself. Even with mirrorless cameras, there can be room for improvement, especially when using DSLR-style lenses via a mount adapter. A bit of fine-tuning or ‘micro-adjustment’ can pay dividends.
