I am using a nikon d800 with nexus housing, 20mm f/2.8D and 170 port for wide angle shots. PQ are good, only the corners are a bit blurry.
Thinking to switch to a 230 port to improve the corners sharpness and with the new 20mm f/1.8G, but there is no way to find any information which extension should I use. Is there any way to calculate the size of the extension? Or any suggestion on the size I should try?