Specifically, Sigma says the Manual Override (MO) function on its lenses is unavailable on the Canon 5D Mark IV for the time being. Full-time manual mode, however, is fine and working perfectly, as you would expect.
In addition to the focusing issues, Sigma says almost all in-camera lens corrections settings that Canon offers on its 5D Mark IV (and other DSLRs) should be disabled, as they are not properly supported and can yield incorrect results, if any at all. These settings include Peripheral Illumination correction, Chromatic Aberration correction, Diffraction correction and Distortion correction.
This isn’t the first time Canon cameras and Sigma lenses haven’t played well together. After the release of the Canon 1DX Mark II, a handful of users noticed issues with Sigma’s Art series lenses, where strange rings would appear on the image as a result of a messed up lens correction mode.
There’s no word yet on when these issues will be addressed, either by Sigma or Canon. But if the last Canon/Sigma incident is anything to go by, there should be a firmware update to fix the issue very soon.
In the meantime, your best bet is to make the most of the lenses and camera if you have any combination that may be affected by these issues. If you come across the problem, adjust your settings accordingly and hope the issue is resolved quickly.
