The Sea&Sea Correction Lens - coming back?

I think this kind of solution is expensive and not effective

In many cases poor performance is due to lenses focussing too far requiring domes too large or even more common incorrect calculations of the position of the dome

I have not had an issue with edges moving from MFT to full frame the key is to choose the right lens

I've got no personal experience of the S&S but I seem to remember a number of folks using them and being happy with the results especially, if I recall right, using lenses like the Nikkor F 16-35 and Z 14-30. 

Good though you've had no issues.  Good choice on those lenses!

I agree with 121 that proper port size and extension length are required for best corner results and of course full frame suffers more than sub full frame given the same F/number. However I have done a number of tests using like equipment, example Tamron 17-28mm and Sony FE 16-35mm PZ in 180mm dome with and without the S&S conversion lens and the S&S always bests the native lens by at least one stop. I have also used the S&S lens on fixed lenses like Zeiss Batis 18mm with similar results.

I also agree with 121 bout minimum focus the Sony 16-35 PZ minimum is 24cm, Tamron 17-28 is 19cm and the Sigma 17mm F/4 has a minimum focus of 12cm. For wide rectilinear I would chose the Sigma 17mm over the other two even without the S&S because of the close focus. It is outstanding in a 180mm port but I have also used it in a 140mm port because it can focus closer than most fisheye lenses. 

To get a one stop increase for $600.00ish is the question and it appears that several have found this worth the cost especially if the alternative is an expensive water contact lens.

The second issue is if you are on team rectilinear or on team fisheye. Many would rather just go fisheye to reduce corner issues.

Image is the Sigma 17mm F/4 in the 140mm dome port at F/11 with the port glass touching the pool light glass, A/V light.

Guys - I've set up a thread for this now......