Usable range on FX will be based on having a dome with a removable sunshade. This will be needed from 8mm through to around 13mm.
On DX, the lens partially vignettes at 8 and 9mm, before offering usable image from 10 through to 15mm.
Pool testing on Sunday....
Isn't the vignetting caused by the fact that the dome is not in the propler location and the lens is seeing the backing plate for the dome?