[kuschku]

It is possible, and that's how broadcast lenses implement it. Sony even sells a 500$ super35 lens that's parfocal (the SELP18105G which was the kit lens for the FS5).

The same compensation behaviour can be done in reverse to prevent focus breathing (and yes, that 500$ lens does that, too).

Sadly outside of Sony's 18-105G, 18-110G and 28-135G, most lenses for mirrorless or cinema cameras are designed to be manual and don't even attempt it.

[namibj]

Strange. We had the tech in the 90's, they were called camcorders. We had it in the 00's, they were called point-and-shoot cameras. I know around 2010 Canon's point-and-shoot cameras, at least some compact stylish consumer ones, knew their focus, on top of being able to reel in the lens to stow away when not in use.

Weird that there are no 3rd party lenses that exploit "software"/"motor" to escape the parfocal optics restrictions while properly exploiting the short backfocal distance of something like Sony E-Mount (vs. e.g. EF-S). With the ultrasonic, very fast AF motors, they can't tell me that an encoder ring for focus pull haptics in lieu of camera-side controls designed for the task would suffer too much input lag. And at the better quality end, the freedom from decoupling zoom and focus should make up for the cost of putting a motor inside, instead of just using an external remote focus pulling clamp. (That said, just adding a focus ring rotation sensor to offset the AF might even be possible to hack onto an existing lens, depending on the AF motor control scheme. A tiny dongle on the side near the base where one doesn't grip seems unintrusive to me.)

[tcbyrd]

It’s an example of lenses designed for different workflows. Film style shoots it’s not uncommon to swap out a lens in between shots, and focus is sometimes a creative choice. Autofocus doesn’t work when you actually want to shift the focus from one actor to the next without them or the camera moving. You need manually focused lenses with precise control of the focus ring. With touch screens you can get close, because you can tell the software what subject to track, but a good focus puller that’s following the emotion of actors is tough to recreate in software. This is also why they’re generally not designed to be parfocal. Film shoots very rarely zoom the lens while recording.

[namibj]

Modern electronics can easily offer ring-to-motor latency low enough to elude perception (though they likely won't go for a truly imperceptible latency, that wouldn't be out of reach), with resolution/step-size competitive with the mechanical backlash of a manual focus ring setup, and the convenience of the focus pulling input knob/ring only having a cable between it and the focus motor in the lens.

If fast (aperture) zoom lenses for sport photography had ultrasonic ring motors for auto focus 10 years ago, at low-to-medium quad-digits for the entire lens, and minimal (AF-included) shutter lag being a major selling point (next to the lack of audible frequency motor noise), there can't be a true technical limitation preventing lenses for "cinema" use from relying on a pair of motors to allow a mechanical/optical coupling between zoom and focus.

I did not mean to use an autofocus on the sensor side; rather just on the actuator side.