Nikolausz

What about video category?

We can have other, more artistic topics such as Golden ratio vs Rule of thirds ("vs" is important) or Can we learn from Renaissance portrait painters for underwater photography? etc. We can probably expect less active discussion.

Yes, but We are gear-heads and we like to discuss technological details of various equipment used underwater. Especially when "vs" is used in the title we can expect a long discussion. Even if the conclusion is that there are more important aspects of photography/ videography than incremental improvements of the hardware it's still fun to discuss it.

My conclusion was that you should spend lots of money for some marginal improvement in some area of photography/videography.

I think we're more strict regarding sharpness than the marketing people of these companies. I use AOI UWL-03 wide lens with GoPro 12 and something like 4-6 cm was advertised as I remember. I haven't done any scientific experiments but my footage with Xmas worm filmed approximately that distance was not sharp.

I stayed with APS-C for practical and financial reasons. I had a Sony A6000 with a Seafrogs housing that was a kind of universal, and when I upgraded to A6400 it was still fitting to the old housing. This setup I mainly used for videos. Later I upgraded the housing to a more ergonomic Nauticam housing (used one). I'm quite happy with the video quality and the ergonomics of the housing. I considered only once to switch to full frame. I had a project to film in a lake during night. Switching to FF Sony and finding a proper wide angle rectilinear lens with the fitting dome port in a Nauticam housing would have been a serious investment (probably over 10K Euro). Finally I just bought a 11 mm 1.8 lens to replace the F4 10-18mm lens for this project. As I remember it was below 500 Euro. I'm quite happy with the results. Would a FF camera produce better material? Probably. But not by a great margin and certainly not 20X better. Fast lenses are relatively cheap for APS-C cameras and they can solve issues with low light filming.

This is the first good quality underwater video with X6 from a person who knows how to shoot proper underwater videos :

I would also probably use this camera mainly underwater, so I agree, that this extra lens means that underwater use was seriously considered and designed.

So the question has been answered. Now, the youtube is full with X6 promotion reviews but only very few underwater footage so far. The only longer test is by Hugh Hou (only snorkelling) and the information he has shared is a bit troubling. In order to use the dive case, you have to change the lens on the camera. I think it has to do with the 1 inch sensor and the hyperfocal distance set by the above water lens, plus the dome of the dive case. It will be interesting to see some real scuba diving tests.

I think Insta360 considers third-party manufacturers as competitors. I've just found out that Easydive has also aluminium housing to X3 and X4 (but no support for X5) https://www.easydive.it/en/underwater-housing/360-video-camera I still use my X2 and not yet motivated to upgrade yet.

I'm sure they will develop a new dive housing for this camera. It's just a matter of creativity and engineering.

That's catch 22 I will stick to my small sensor GoPro

In my opinion, when the 1 inch sensors were introduced, they should have also implemented an AF system into these small cameras. I wouldn't call them action cameras but small content creator cameras. Most of them are not used for sport anyway.

A critical problem, in my opinion, is the minimal focus distance with Mission 1. It is way longer than in the case of the black series due to the larger sensor. It will be OK for reef scapes but CFWA pictures will be not sharp. As moving as close as possible, especially in case of lower visibility, it is important for underwater videography to use an additional correction lens. I'm not sure if existing lenses (non or AOI) were compatible or not.

I absolutely agree with your analysis and I came to a similar conclusion. Due to the crop factor, we can forget the ILS version for wide angle (but the mission 1 pro will be interesting). I played a bit with the idea of building a compact macro system around the ILS version, but honestly, it makes more sense to spend the same money on an MFT camera with a properly communicating macro lens with AF. Not to mention that according some rumours, the new Sony RX100 camera with 1 inch sensor is around the corner. Probably a safer bet to build an underwater camera system around it.