Nikon Z Mount
Direct Answer
The Nikon Z Mount (introduced in 2018 for the Z-series mirrorless system) features the shortest Flange Focal Distance (16.0 mm) and the widest inner throat diameter (55.0 mm) of any full-frame mirrorless camera system in history. This extreme geometry enables extreme optical designs, including the ultra-fast NIKKOR Z 58mm f/0.95 S Noct.
Source: Nikon Corporation Z-System Technical Whitepaper / CIPA
Specs
| Flange Focal Distance (FFD) | 16.00 mm (0.630 in — the shortest full-frame FFD in the world) |
| Inner Throat Diameter | 55.00 mm (2.165 in — the largest full-frame throat diameter in the world) |
| Bayonet Tabs | 4 asymmetrical locking tabs with counter-clockwise twist (traditional Nikon direction) |
| Electronic Interface | 11 gold-plated contact pins |
| Max Theoretical Aperture | Up to f/0.58 theoretical optical limit (demonstrated in Noct f/0.95) |
| Legacy F-Mount Adaptability | Nikon FTZ / FTZ II adapter (30.5 mm spacer) provides full AF/AE with AF-S and AF-P NIKKOR lenses |
| Camera Systems | Nikon Z9, Z8, Z7 II, Z6 III, Zf (full frame), Z50, Zfc, Z30 (DX APS-C) |
The 55mm / 16mm Optical Advantage
Nikon designed the Z-mount with extreme physical dimensions: a $55.0\text{ mm}$ inner diameter ($11\text{ mm}$ larger than the historical Nikon F-mount) and an ultra-short $16.0\text{ mm}$ FFD. This allows rear optical elements to sit close to the sensor with huge diameter, eliminating corner ray angle steepness and delivering corner-to-corner edge sharpness wide open at $f/1.2$ and $f/0.95$.
Cross-System Adapter Feat
Because Nikon Z has the shortest FFD of all full-frame mounts ($16.0\text{ mm}$ vs Sony E $18.0\text{ mm}$ and Leica M $27.8\text{ mm}$), third-party adapters (like Megadap ETZ) can adapt Sony E-mount autofocus lenses directly onto Nikon Z cameras using an ultra-thin $2.0\text{ mm}$ adapter ring with full AF-C and eye-tracking support.