I have been doing a day of free-lensing shooting with a Canon 5D mkIII, and on both my photos and videos, there is a perfectly vertical line splitting the picture into two parts, with a small exposure difference between the two parts.
It is subtle on photos but quite visible in video, with the movement and this line still remaining.
Has anyone have ever faced the same problem? How can I correct it?
FYI: I have been using Canon EF 70-200mm f2.8 L IS and Canon 50mm f1.4 USM both with ND filters.