I did a rudementary test with my Fuji 50-140 plus 1.4x & 2x TCs (although not on wildlife) and I found that there was no noticeable difference between TC shots and non-TC enlasrged to the same size on the monitor. What I did think was the extra reach of the TCs (or loner FL lenses) would likley make target aquisition easier with things like birds or small animals so I kept the 1.4x TC for just in case.