The focus distance is reduced by a multiple of 0.71 when my lens is mounted so my EF400mm becomes 380mm and enhances to F2.8. So if I need a better distance I have to invest in a teleconverter 1.4
|The Pied Fantail shot at 25-30ft was rather soft and need some post sharpening and enhancement. Even then no clear feathers to see.|
So far in the real world bird photography using the Viltrox adapter, my general review of the combination of my above set up is a 2.5/5 stars rating. I did not expect so poor resolution from the combination. Contrast was not there. Colors was just lame. Focusing speed was not tact fast enough with plenty of hunting when shooting in low light condition.
Even stepping down to F8 or F9 I still cannot get much resolution out of my OMD-1 mark III. ISO was kept low of Asa800. So my rating is a poor rating for the moment until I do further test with other lenses.
Meanwhile WK Liew have more success with his EF 500mmf4 on his Fuji X-T4 using a Fringer adapter. Maybe it is Olympus smaller sensor or my DO lens is not sharp enuf ...... I got to try out his lens to make sure I am wrong.
As a comparison my XF100-400 with my XE2 body (16mp sensor) fair even much better as shown below in term of feather details. Jpeg without post processing.
|Fuji XF100-400mm with XE-2 body.|