These adapters don’t make the manual-focus lens itself autofocus. Instead, the teleconverter contains its own optical group that can move a small amount for fine focus adjustment. In practice, you first focus the manual lens approximately by hand, then the camera’s AF system drives the teleconverter’s internal optics to “trim” focus more precisely.

So the teleconverter is acting like a small autofocus lens placed between the camera and the manual lens.

Main limitations:

• It only has a limited focus adjustment range, so you usually must get close manually first.
• Autofocus performance is not the same as a true AF lens; it’s more of a fine-tuning system.
• Because it is a teleconverter, it changes the effective focal length and reduces the maximum aperture, which can also affect AF usability and image quality.

Used within those limits, it can be quite useful, but it’s not a complete replacement for a native autofocus lens.