Hi
I find that when using my Fuji 100-400 lens with the matching 1.4X extender at full reach my photos reveal a sort of halo effect around the subjects as shown in this small section of a recent picture.
The photo was taken a 1/1000th hand held and I have tried keeping the OS on and OS off, but with no difference. I have no problems when not using the extender and get pin sharp pictures throughout the range
Any thoughts and ideas would be welcome