Some of the best photos hanging on my walls were taken with a Nikon F3 and 1980's vintage manual focus lenses. This is the equipment I used until 2009.
Shooting manual focus macro is not hard. I used an Ikelite underwater meter at get my exposure, then I would set the focus using something at the same distance. Then I would get the subject in the viewfinder and move closer until it was in focus and take the shot. Getting the ficus right while close to the subject would take to much movement for many subjects.
Wide angle with a dome was simple. The focus is set to the false image projected by the dome. Unles you are trying close focus wide angle you shouldn't need to touch the focus after setting it early in the dive. After that it is all about lighting just like recently manufactured equipment.
Shooting manual focus macro is not hard. I used an Ikelite underwater meter at get my exposure, then I would set the focus using something at the same distance. Then I would get the subject in the viewfinder and move closer until it was in focus and take the shot. Getting the ficus right while close to the subject would take to much movement for many subjects.
Wide angle with a dome was simple. The focus is set to the false image projected by the dome. Unles you are trying close focus wide angle you shouldn't need to touch the focus after setting it early in the dive. After that it is all about lighting just like recently manufactured equipment.