For components related to AXIOM Beta see - Parts:Enclosures and Associated Mechanical Parts.

1 Overview of Lensmounts

This page contains information about the different lens mounts and the protocols used to communicate with the attached lenses.

1.1 E Mount

Seems to be a good choice because there are adapters available for almost every camera/lens type for reasonable cost. Even active mounts for Canon EF, etc.


  • Outer diameter 46.1mm
  • Flange focal distance is very short: 18mm
  • Frame size APS-C, 35mm


  • Short flange focal distance allows mechanical adapters to cover pretty much any lens mount out there
  • widely adopted


  • not an open standard
  • licensing necessary for lens communication protocol -> reverse engineering required
  • using stack adapters reduces the accuracy and ruggedness of the whole system

LexOptical E-Mount on Github - A work in progress reverse engineering of E-Mount communication protocol.

Sony opens E-mount specifications. Seems we are on the safe side with using an E-mount adapter...

1.1.1 E-Mount Bayonet Scans

E Mount Bayonet Main.jpg

E Mount Bayonet 2-small.jpg

E Mount Bayonet 3-small.jpg

Full 4800 DPI scans available for download at:

Screws are 1.6mm outer thread diameter so could be M1.6, screw total length is 5,75mm

1.1.2 E-Mount to EOS Adapter *Inside*

Inside of our E-mount to EOS adapter sample

E-mount-EOS 01.jpg

µC Board to translate from Sony E to Canon EOS

E-mount-EOS 02.jpg

EOS contacts with springs on the PCB side

E-mount-EOS 03.jpg

E-mount-EOS 04.jpg

JL ... position of the EOS mount contact springs

We can replace this board with our own adapter board to connect to the cameras I/O's

1.1.3 Passive EF Mount

1.1.4 Active Canon EF Mount

  1. body <-> lens communication protocol:
  2. pins and contacts:
  3. EF-S protocol:

1.1.5 Nikon F-Mount

Nikon-bayonet01.jpg Picture of Nikon F bayonet mount components.

Measured Bayonet Thickness: 1.3mm

  1. general information:
  2. body <-> lens communication protocol:
  3. technical drawing of F-mout

1.1.6 Micro Four Thirds Mount

  1. body <-> lens communication protocol:

1.2 Open standard Mount

P+S Technik offers with their IMS mount an open standard. For AXIOM Beta the adapters are too expensive, but for sure an option for AXIOM Gamma.

Is there a affordable really open standard mount out there?

please add it here...

1.3 Talk with a Canon Lens

Research links for the Canon EF-S Protocol

Electronic follow focus experiment

AXIOM Beta is a professional digital cinema camera built around FOSS and open hardware licenses.

AXIOM Remote is designed to be a comprehensive remote control unit for the AXIOM Beta range of cameras

How to Contribute - Growing and improving documentation is an ongoing process and you're very welcome to contribute to the project by helping to make these archives better for everyone.