Micro Four Thirds flange focal distance
The Micro Four Thirds mount (Mirrorless 4/3in) has a flange focal distance (FFD) of 19.25 mm as of 2026-09-12, the fixed distance from the lens mount's flange to the sensor plane, set by that mount's published engineering specification. This value does not change between camera bodies that share the mount.
Worked spacing example
Using only the Micro Four Thirds flange-to-sensor distance as a one-component train against BackfocusLab's own 55 mm T-thread example target (filter correction off), the Micro Four Thirds camera needs about 35.75 mm of added spacing to reach that illustrative 55 mm target. This is an example, not a requirement for your specific reducer or corrector, always use the distance your optical component's manufacturer specifies.
- Flange focal distance
- 19.25 mm
- Mount type
- Mirrorless 4/3in
- Example target (T-thread convention)
- 55.00 mm
- Spacing gap at that target
- +35.75 mm
Other mounts
Source
Flange focal distance is a published mount-design constant, not a measurement made by this site or specific to any single camera body. Verify the exact figure against your camera manufacturer's official specification before ordering adapters; small manufacturing tolerances exist. Method 1.1.0. Reviewed 2026-09-12.