Nikon Rumor 在發表當天就有說了，應該是在研發新的自動對焦系統。
下面是原文。
https://goo.gl/J8WaV4
Today Sigma announced the price and availability of their new Sigma 70mm f/
2.8 DG Macro Art full frame lens that will be available for Sigma, Canon and So
ny E mounts but not for Nikon F-mount. The reason is because Sigma is using a n
ew autofocus motor?(similar to the Nikon AF-P lenses). Here is the exact quote
Sigma's CEO Kazuto Yamaki gave Focus Numerique in an interview a few months ago
: