Last week, Sigma announced that some prime lenses are not fully compatible with Canon's 1D X Mark II. They have discovered some metering, manual focus, and lens correction performance errors. This announcement from Sigma describes the issues further:
We have found that some Sigma interchangeable lenses for Canon are not fully compatible with the new CANON EOS-1DX Mark II, which was released on April 28th.
When certain lenses are attached to this camera, exposure of the image may not be accurate.
We are sorry for the inconvenience, and we will make a further announcement on our website when specific details are finalized.
In addition, please also refer to the below usage notice related to this announcement.
Phenomenon
When the lenses listed below are used and either "Evaluative Metering" or
"Center-weighted Average Metering" is selected in Metering Mode of the camera,
the image could show some underexposure.
Products concerned
SIGMA 20mm F1.4 DG HSM | Art
SIGMA 35mm F1.4 DG HSM | Art
SIGMA 85mm F1.4 EX DG HSM
We are currently working on the firmware update for respective lenses, and the release dates will be announced later.
Usage Notice for customers who are using EOS mount SIGMA lenses on a CANON EOS-1DX Mark II:
・ MO (Manual Override) function is unavailable with this camera (Full-time Manual function can be offered).
・ When using a SIGMA interchangeable lens for EOS, setting the corrections to "Disable" is recommended, as "Lens Correction" functions of the camera, such as Peripheral illumination correction, Chromatic aberration correction, Diffraction correction and Distortion correction, are not supported. If those functions are activated, the performance of lenses may not be accurate.
This is not only for EOS-1DX Mark II, but also other camera bodies.
We appreciate your continued support for our company and products.