1 hour ago, JayceeB said:

I haven't been able to find a way to turn off lens correction in camera. You can turn it off in Lightroom after importing, but Lightroom defaults to applying it. I prefer lens correction on for the 20-50mm and 14-35mm, but lens correction off for the 8-15mm fisheye.

Lightroom only applies settings like this if you configure it to do so. You probably experimented with import settings and it's been set to do Lens Corrections ever since. Fortunately it's easy to change.

"I think, the marelux 180 glass dome or their 210 acrylic will not add much volume or load and dramatically improve lens performance."

@Adventurer

I'm considering the 180mm. I haven't had great luck with larger acrylic domes, as the ones I've used require weight to keep them from nosing up.

"I assume the freshly introduced Marelux Aquista 135D - which is Marelux‘s take on Nauticam‘s WACP lineup - will give you the highest image quality with that lens," @Adventurer .

For me, the improvement in image quality would need to be significant to justify the cost and heavier weight (for shore diving) of the Aquista 135D. A little out of my budget for testing purposes. I'm interested to see the results though, once someone is able to test and report back.