Auto focus seems to be getting worse over time

[vigilante]

Is there anything in general I can do to improve auto focus?
The camera is not a high end one, neither is the lens, but I could swear the focus worked much better in the past.

It's nearly impossible for a shot of a person's face to be in focus. When I look through the viewfinder, the small viewport does seem like it went in focus. It's only later when I look at the full quality shot on a larger screen I find that it's not in focus.

Similarly if I'm shooting by using the touchscreen, it may appear to have got the right focus, but it turns out bad too.

The only way I've found to really get a tight focus is by using touchscreen and zooming in tight and then doing manual focus to where I want. This really only works for fixed position of camera and subject though.

So my question is, do lenses or cameras just "wear out" with their auto focus abilities? Or is there something I can calibrate or clean or reset etc? Is this mostly an issue of the camera, or of the lens? If I buy a better lens, will this fix auto focus?

Any ideas?

 

[KmH]

So. What make/model camera is it?
How well has the camera been stored/maintained?

Most DSLRs have the AF (Auto Focus) module in the bottom of the camera under the main mirror box.
Part of the main mirror that reflects the light from the lens up to the viewfinder is 50% transparent.
Light from the lens that passes through the main mirror is reflected by a secondary mirror down through a clear window to the AF module in the bottom of the camera.

For most still photos the AF module uses phase-detection to determine when focus has been achieved.
If the secondary mirror, or the window in the bottom of the mirror box between there and the AF module is dirty AF performance may suffer.
Additionally a jarring impact could knock the AF module out of alignment.

The bottom line is the camera may need to be serviced by a qualified facility.

 

[astroNikon]

As mentioned, more specific make/model information is needed.

For instance, if you dropped your DSLR at some point it may have dislodged the mirror slightly, which as stated above is involved in providing the image to the AF module to focus. So, with a slighted mirror you can lose AF accuracy.