Sigma is to provide a free firmware update for Nikon Df owners using Sigma lenses.
"We have found that the current firmware of our Nikon fitting interchangeable lenses may not work properly with the Nikon Df camera's OS and Auto Focus functions." Sigma stated.
The issue effects lenses that don't have an internal AF filter, as well as those that do. The affected lenses are as follows:
8mm F3.5 EX DG Circular Fisheye
15mm F2.8 EX DG Diagonal Fisheye
20mm F1.8 EX DG Aspherical RF
24mm F1.8 EX DG Aspherical Macro
28mm F1.8 EX DG Aspherical Macro
Macro 50mm F2.8 EX DG
Macro 70mm F2.8 EX DG
For lenses that are compatible with the Sigma USB Dock, it is possible to update the firmware via Sigma Optimization Pro. For discontinued products, please contact your nearest authorized Sigma distributor for further details.
For more information, take a look at the Sigma website