P4k App and touch focus question

So the P4k has tocuh focus but it hunts, which doesn’t work in production situations. So here’s my question:

Could an app be developed where a user focuses on on part of the image, sets an A mark , touch focus to another point, set a B Mark, and then just switch back and forth from the A mark to the B Mark based on the mathematical focus position, not the in cameras contrast detection?

The Aputure DEC Lens Regain can do this so it's completely possible to do with software provided that BMD's camera control API allows you to control focus. I'm forgetting if it does or not.

It would be a cool feature for future firmware.

A Bluetooth Camera app could perform this function with great sophistication by setting soft stops at any number of points similar to but better than a conventional follow focus. However it would fail to be effective if the subjects fail to meet their marks.


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I've just looked into the developer manual. Focus can be set as a fixed point 16 bit integer. So theoretically it should be possible.
Display brightness could also be set (if you want to toggle fast between lowest and highest screen brightness).

When I first got my GH5, I thought this was a killer feature. In practice, I've almost never used it in real life. But, I like to shoot quite shallow, and work with actors that move naturally, not be robots that hit exact marks.

Conventional focus pulling is not effective if the subject fails to make their marks.

I didn't know the Aputure Lens Regain does something similar - I've been considering that over a Speedbooster because of the lens control.

A focus mark app is likely to be used at f/4 and above - I prefer more shallow, too, but sometimes it's overkill.