M42×1 screw mount to Micro Four Thirds adapter thickness
A glassless M42×1 screw mount to Micro Four Thirds adapter must be about 26.21 mm thick to keep a M42×1 screw mount lens focusing correctly on a Micro Four Thirds body. This equals the M42×1 screw mount flange focal distance minus the Micro Four Thirds flange focal distance, both published mount-design constants, reviewed 2026-09-12.
How this is computed
Using the M42×1 screw mount flange-to-sensor distance as a one-component train against a backfocus target equal to the Micro Four Thirds flange focal distance (filter correction off), BackfocusLab's own model reports the spacing gap between them as the required adapter thickness.
- Source mount (lens side)
- M42×1 screw mount, 45.46 mm FFD
- Target mount (body side)
- Micro Four Thirds, 19.25 mm FFD
- Adapter thickness
- 26.21 mm
This is illustrative arithmetic, not a substitute for the manufacturer's own adapter specification; small machining tolerances exist. A dumb, glassless adapter only forwards the mechanical mount; it makes no claim about autofocus, aperture control, or electronic contacts, and a nominal fit is not a compatibility guarantee. Verify against your camera manufacturer's published specification before ordering.
Open the workbench and enter your own train