portrait with E M-5 and Kenko 400
At that focal length I would think the old focal length, shutter speed ratio would apply. I.e. focal length of 400 would need a 'minimum' of 1/400s. At the very least. That's assuming you are hand holding.
If you took this shot with a tripod, then, well, yeah, the lens seems to have quite a bit of IQ limitations.
Can't tell how you took the shot except that it was taken with a 1/300s shutter speed.-- hide signature --
took this photo hand-held- didn't want to use a higher iso - figured that ibis would help.