incase anyone's interested...


I found a way to answer the question myself - just found an undistorted image from my collection and applied the 15mm profile to it


my conclusion; unacceptable quality loss (in the corners) unfortunately, even when you limit the distortion correction to 50%. The CA is hugely amplified and the image becomes VERY soft in the corners - this was starting with a Sigma 50mm f/1.4 set at f/11.


I think I'll be going with the 17-40mm, maybe get a dedicated fisheye further down the line