Wide converter for gopro's flat port?

[tamas970]

I know this is not the videography thread but optics are optics
I would like to improve my Hero4's image quality and underwater FOV. As probably everyone knows, gopro uses a flat port in the dive
housing - besides, a simple dome wouldn't work, because the lens is not focusable.

Inon came up with a gopro specific solution, the UFL-G140 SD, which is a bit pricey, if you have to buy the cage as well, it puts u back 500+$.

Is there a viable alternative? The stock lens with its 170°FOV is a challenge to serve (and a shame to leave behind a flat port) i know, but
could someone use a decent M67 wide converter to boost corner IQ+FOV?
What does a regular wide converter, such as the inon UWL-H100 do with the minimum focus distance? (the minimum focal distance is the
reason that normal domes and wetmate/bigeye type simple air lenses are ruled out)

I am also planning to replace the stock gopro lens to a 3.6 or 4.2mm unit, which might be easier to provide with a wide converter I guess...

 

[Interceptor121]

Inon produce the UWL-H100 if there was a solution to reuse certainly they would have done it
I imagine that lens vignettes an awful lot
Their new solution seems neat and effective and you can also attach a close up lens

Besides 94 degrees in water for video is plenty. The issue is not as much the field of view is the quality at the edges that is bad I guess this set up corrects it

 

[tamas970]

Exactly, the edge quality was my first concern, 90-100°FOV is good enough for me. 140° is probably too much, I don't dive
everyday with whalesharks and Titanic-size wrecks. That's why I am thinking on a ~4mm/100FOV on air lens replacement
for the camera. However this is still broader than the lenses compatible with normal wide converters...

Besides 94 degrees in water for video is plenty. The issue is not as much the field of view is the quality at the edges that is bad I guess this set up corrects it