Nikon issues firmware updates for Df, D5200 and D3200

I was wondering the same.

Sigma and Nikon seem locked in an arms war, with Nikon’s camera firmware updates crippling Sigma lenses’ AF, and Sigma’s lens firmware updates undoing the sabotage.

See here if this is news to you:
http://www.dpreview.com/news/2013/11/19/sigma-issues-advisory-on-lens-compatibility-with-nikon-d5300

The Nikon updates have also blocked use of 3rd-party batteries. Pure hostility toward the end user.

I respect Nikon’s heritage and technical prowess, but their recent contempt for their own paying customers is despicable.

Source Article from http://www.dpreview.com/news/2014/01/22/nikon-issues-firmware-update-for-df-d5200-and-d3200