A7III - way to step manual focus 3rd-party lenses by wire without touching the lens

[Dory]

Hi everyone, first time here - but not first time Sony Alpha user. I have a problem that seems to be pretty basic, but could not find an answer for the life of me.

I have a Sony A7III (newest firmware 3.10), which I use for nightscape photography a lot. Like many other Milky Way shooters on a budget, I use the venerable Samyang/Rokinon AF 14mm f/2.8. The lens is optically perfect, but the manual focus-by-wire ring is pretty much unusable for astro. I've been looking for a way to control the lens' focus but without having to use the focus ring on the lens. So far I have tried:

• Digging through the menu system and custom buttons to see if there's an option to map a dial to manual focusing, without success.
• Finding a wired remote, but so far could not find any wired remote that allows manual focusing.
• Pairing with a phone and control from phone, but Imaging Edge Mobile doesn't support focus adjustment.
• Buying the RMT-P1BT bluetooth remote, which refuses to work with the Samyang. When I tried to press the + or - buttons to adjust focus, the focus scale does show up on the LCD, but the lens doesn't do anything (and I tried in MF, DMF, and AF-S modes). When switching to AF-S, half-pressing the shutter button on the remote does autofocus the lens. When I tried this on MF mode on a Sony lens, however, manual +/- focus adjust using the remote works fine.
• Using Imaging Edge Desktop shooting tethered to a computer: this has the same issue as with the Bluetooth remote, i.e. manual focus adjustment works fine with Sony lens, but not with the Samyang.

One thing that I did not try is upgrading the lens' firmware. My lens' firmware version is v21, and I see that Samyang has v23 available. However, I do not have the Samyang lens station, and couldn't find release notes of v22 and v23 firmware so I'm not sure if this will fix the issue, or if I'll end up with a USB paperweight.

So my questions are:

1. Has anyone succeeded in finding a way to manual focus of third-party lenses on this A7III without using those lenses' manual focus ring? Am I doing anything wrong here?
2. Otherwise, does anyone have the Samyang/Rokinon 14mm AF on firmware v23, who is kind enough to try using Imaging Edge Desktop or Sony bluetooth remote and see if manual focus works with your lens?

 

Edited April 9, 2020 by Dory