Are Canon EF mount mechanical drawings available, or do I need to reverse-engineer one?
Asked 3/25/2018
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I want to build a simple DIY lens and need accurate dimensions for the Canon EF mount on both the camera and lens side. I’ve searched for official drawings but mostly found discussion about whether the EF mount is proprietary, not the actual dimensions. Does Canon publish mechanical drawings for the EF mount, or is reverse engineering the only practical option? If official drawings are not available, is it better to measure an existing mount or reuse parts from extension tubes, broken EF lenses, or old EOS film cameras?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
8y ago
2 Answers
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Where can I find a mechanical drawing of the Canon EF Mount?
If you mean one published by Canon, you won't. They consider such information proprietary. You'll either need to measure and 'reverse engineer' the pieces yourself or find someone else who has - and is willing to share their results with you.
With the ubiquity of the Canon EF system, you'd probably be much better off just buying a few budget bin broken "parts only" Canon EF mount lenses and take the mount bayonets off of them. On the cameras side: there are tens of thousands of old EOS film cameras that sell for less than $25.
Use those instead of trying to make your own.
A machinist will likely cost considerably more to produce the same thing.
Originally by user15871. Source · Licensed CC BY-SA 4.0
user15871
8y ago
0
Generated from our catalog & community — verify before relying on it.
Canon does not publicly publish EF mount mechanical drawings. The mount design is generally treated as proprietary, so if you want exact dimensions, the practical options are to reverse-engineer an existing mount or use donor parts.
The easiest route is usually not machining a new mount from scratch. Community advice suggests salvaging the bayonet from inexpensive broken EF lenses, extension tubes, or even old EOS film cameras, which are often cheaper and more accurate than paying a machinist to fabricate one.
That also avoids fit issues: EF compatibility involves both the mechanical mount and, for electronic operation, Canon’s reverse-engineered communication system used by third-party makers.
So for a DIY lens, the best approach is:
- don’t expect official Canon drawings,
- measure an existing EF mount if you need dimensions,
- or better yet, reuse an existing EF mount component from donor gear.
If your lens will be fully manual, reusing a donor mount is usually the simplest and most reliable solution.
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