Definition
Distance from the lens mount to the camera sensor.
Common flange distances
| Mount | Flange (mm) | Sensor | Sensor size (mm) |
|---|---|---|---|
| B4 | 48 | 2/3” | 8.8x6.6 |
| Canon EOS-M | 18 | APSC | 22.2x14.8 |
| Canon RF | 20 | FF | 24x36 |
| Fuji X | 17.7 | APSC | 23.6×15.6 |
| Leica M | 27.8 | FF | 24x36 |
| L Mount | 20 | FF | 24x36 |
| MFT | 19.25 | M4/3 | 17.3x13 |
| Nikon Z | 16 | FF | 24x36 |
| Sony E | 18 | FF | 24x36 |
Source :
Flange focal distance - Wikipedia
Image sensor format - Wikipedia