8" dome with a cropped sensor

Hey guys, tried searching for this.

Currently shooting a cropped sensor Canon SL2 with a 15mm 2.8 Canon lens. The ikelite housing comes with a 6" dome port, but I can't help but wonder what like would be like with an 8" dome port...

I understand the physics and differences between both.

My main question is, with a cropped sensor and a relatively not that wide angle(f22.5 equivalent), would I really even be able to take advantage of an 8" dome port? Would it add that much more scene coverage? I know it will help with split shots and corner sharpness.

Any input would be great! I'm really enjoying the set up, but I've been thinking about this pretty frequently. It's also a big cost and size difference, just to try out.

Thanks!

Michael

https://www.flickr.com/photos/fifinator/

Although from a manufacturer from a different port, he is an honest bloke and the pictures showing the coverage are genuine. (scroll down a bit)

http://uwcamerastuff.com/precision_5_dome.htm

That's the fisheye lens? The port charts recommend the 8" dome port 75340 with no extension. Fisheye lens are not as sensitive to dome size as rectilinear lenses as they are designed to focus on a curved 180° image so normally the answer is a bigger dome does not help much. However the 6" dome centre of curvature is 1" closer to the camera so presumably the entrance pupil of the lens is 1" forward of the centre of curvature with the 6" dome. So the optics of this combination may not be as good. Here is a link to the port charts for ikelite:

http://docs.ikelite.com/reference/port-chart-dl-system.pdf

I used a sigma 15mm for a while in a 5503 dome port (the 6 inch), and later got the larger 8 inch port. I never did any side by side comparison shots.

the wide angle ones in this set and the years before are with the smaller dome port. I got the bigger dome port in 2010 I think, so after that I used that port mostly. Think I sold the smaller one because I never used it anymore.

https://www.flickr.com/photos/cerianthus/albums/72157604579637384

Not quite apples to apples, but I recently tested Sony 10-18mm and 16-50mm in 6" and 8" domes, side by side at various focal lengths and apertures, and found very little difference between 6" and 8". You can see the results here.

Ok guys I've gotten some good information. Sounds like dome port is not needed. I have no problem with split shots an I find my shots to be pretty sharp. Everyone has told me a wider lens is more worth the investment. With a cropped sensor, looks like I'll only be able to go for a 10mm.

Thanks for all the input. Doesn't look like a 8" is worth getting considering the size and added cost.