Lens Mounts

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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: http://files.apertus.org/AXIOM-Beta/e-mount-scans.zip

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: http://www.magiclantern.fm/forum/index.php?topic=3796.0
  2. pins and contacts: http://en.wikipedia.org/wiki/Canon_EF_lens_mount
  3. EF-S protocol: http://pickandplace.wordpress.com/2011/10/05/canon-ef-s-protocol-and-electronic-follow-focus/

1.1.5 Nikon F-Mount

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

Measured Bayonet Thickness: 1.3mm

  1. general information: http://en.wikipedia.org/wiki/Nikon_F-mount
  2. body <-> lens communication protocol: https://nikonhacker.com/viewtopic.php?f=8&t=1437
  3. technical drawing of F-mout http://en.wikipedia.org/wiki/Nikon_F-mount#mediaviewer/File:Nikon_F-mount_mechDwg.png

1.1.6 Micro Four Thirds Mount

  1. body <-> lens communication protocol: http://preamp.org/revenge/four-thirds-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