On autofocus and why the camera stops hunting

One of the unexpected effects of using the OP7 close focus conversion lens isn't the magnification.

It's autofocus.

After using it for a while I noticed that continuous autofocus became calmer.

Once locked onto a subject, it was less likely to hunt. Even if focus was briefly interrupted by a leaf or a stem, it often returned directly to the subject instead of sweeping towards infinity and back again.

At first I assumed this was camera-specific.

Then I noticed similar behaviour across different cameras.

The reason is surprisingly simple.

A normal lens can focus anywhere between its minimum focusing distance and infinity. If autofocus loses confidence, it may need to search through that entire range before finding the subject again.

A close focus conversion lens compresses that range.

Instead of focusing from nearby all the way to the horizon, the lens now operates within a much smaller working distance. Infinity has effectively moved to arm's length.

The autofocus system no longer asks:

"Is the subject half a metre away? Two metres? Infinity?"

It only asks:

"Where within this small region is focus?"

At the same time, the shallow depth of field creates stronger visual separation between what is in focus and what is not, giving the autofocus system clearer information to work with.

Nothing about the autofocus motor has changed.

Nothing about the autofocus algorithm has changed.

Only the optical search space.

The result isn't perfect autofocus.

It's simply a smaller problem to solve.

Less hunting.
More following.

A close focus conversion lens doesn't make autofocus smarter.

It simply gives it a smaller world to understand.