Nikon’s Nikkor Z super telephoto lenses are fantastic pieces of kit, there’s no question. For what they cost, you’d expect them to be pretty spectacular, too. Like most modern autofocus mirrorless lenses, though, they use a focus-by-wire system when manually focusing. Focus by wire lets you make big adjustments by turning the ring quickly or fine adjustments by turning it slowly. A fantastic innovation for photographers, not so much for filmmakers.
So, Nikon has released new firmware for their 400mm f/4.5 VR, 400mm f/2.8 TC VR, 600mm f/4 TC VR and 800mm f/6.3 VR lenses to bring linear focus to the focus rings of those lenses. This lets them be used in video rigs with follow-focus units with the certainty that they’ll nail the target every time.