[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.