pdk42
Moderator
I recently had a short foray back into m43 (part of planning my Japan trip) and while I had the camera (an EM1.3) I tested a copy of the Olympus/OM 100-400 (which clearly is based on the Sigma 100-400 for FF). In general I was very unhappy with the lens's performance, but what was very clear to me was that it delivered reasonable results at shorter distances but was pretty awful towards infinity. I found exactly the same with the Panasonic 70-300. In both cases I was doing my tests in cold winter conditions (shooting winter trees on the horizon) so I don't think atmospheric issues were at play.It's interesting how we can reach different conclusions on lenses. I have found the resolving power of the 70-300 to be quite good, and Richard found the same in his review. But Charles and Paul reached a different conclusion.
Interestingly though, I found significant focus wander on both lenses (OM 100-400 and Panasonic 70-300) when shooting near infinity. I wonder if that's what different people are reporting. Those who shoot these lenses at short-medium distances, perhaps using burst modes (where focus wander is disguised in the glut of frames), find that they perform OK. Whereas people like me who generally shoot things far away on single shot mode find that they get a lot of virtually useless images.