Sea Frogs Sony a7riii housing review?

Barmaglot_07 wrote:

Just had a thought - they do have a focus gear for the 90mm macro lens, which is basically a long cylinder with gear teeth at the base, since the focus ring on SEL90M28G is way out there at the end. Now, looking at specs, SEL1635Z is 98.5mm long and 78mm wide, while SEL90M28G is 130.5mm long and 79mm wide. The zoom ring on 1635Z is about halfway up the lens, so I'm thinking - if you take Meikon's focus gear for 90mm and wind a little tape around the focus ring on the 1635Z, it should be able to grip it without issues, and it should clear the focus ring further up the lens. Now, I don't know exactly how long that zoom gear is, so if it's actually longer than the 1635Z, you may need to cut it down to size, but if it's not too long, you might be able to get away without any non-reversible modifications.

Sea Frogs won't sell the gear alone, so I would have to buy it with the port for $189 - a little expensive for an experiment.  Plan B would be to cut my own gear out of plastic on my mini-mill.  The zoom rotates less than 90 deg, so that's only 20 teeth on a 3 mm pitch.  Plan C would be to buy a flexible plastic timing gear track for $30 and wrap it around the 16-35 mm.  Plan D, sell my a7Rii, buy an a7Riii and new housing to get 28-70 mm zoom isn't acceptable.  Plan E would be to live with fixed focal length.   Plan F, buy an Ikelite system for around $3800 has already been dismissed.