Archibald wrote in post #17685811
f/16 is too small and incurs diffraction softening ... not sure if that explains anything.
It sure does, it's the entire problem with that photo**. There is no motion blur there at all, and perfect textbook diffraction blurring. With the 7D mk II, the effects of diffraction show up at a larger apertures than on almost all other Canon DSLRs except for the T6i/s . Sharpness is going to peak with most lenses on the 7D2 at f/5.6 of f/6.7. Above this, things go slowly but steadily downhill. By f/16, it's pretty bad. I found that that shooting with my 60D and 70-300L combo that f/6.7 was the sharpest, f/11 was the limit of what I could make acceptable with sharpening, and photos beyond this were just too noticeably soft to fix.
**Or nearly so. Seeing that it was shot towards the long end, and with a 1.4x TC, that is going to contribute a little too. Extension tubes would be the preferred means of getting closer for a higher magnification.