This is my first question-post. First of all my final goal is to build a simple but functional objective. I was inspired by this video: DIY Camera Lens (I don't hope to make something so neat the first time.)

I decided I shoud start by building my own EF mounts (or rather have a mchinist build EF mounts) and I can't find specific information on the dimensions of EF mounts (body and lens sides) where to start. I know I could always measure the mount, but a comprehensive drawing would be better. Does anyone have some insight on where to find such data on line?

This question popped on my searches up: Mechanical drawings of lens mounts: are they “open source”?, but most answers deal with the opensourceness of the EF mount and not provide any drawings.

Another option I thought of is using one of the sides of extension rings. And only dealing with the thread.

Thanks for your time!

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    I suspect that that is considered Canon's proprietary information, although it's obviously available via some sort of agreement with them, because there are third-party manufacturers of EF mount-compatible lenses. You might try contacting Canon to see if they have any arrangements for licensing/releasing those specs to individuals as opposed to corporations... – twalberg Mar 25 '18 at 21:36
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    Not really an answer, but it might be easier to buy an adapter for M42 and have your machinist make an M42 mount. – Peter Taylor Mar 25 '18 at 21:36
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    @twalberg There's not necessarily any agreement between Canon and third party lens makers. In fact, I would be quite surprised if Canon provides any technical information to third party lens makers. It's called "reverse engineering". – Michael C Mar 26 '18 at 0:44
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    Possible duplicate of Mechanical drawings of lens mounts: are they "open source"? – mattdm Mar 26 '18 at 1:41
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    I would strongly urge you to re-phrase the question as: "I want to make DIY lens for canon EF mount, what are the starting points? I have read X, Y, Z websites, but still think i need to get a schematics of the mount to start". Have you seen this website, for starters? diyphotography.net/build-your-own-lenses – aaaaa says reinstate Monica Mar 26 '18 at 3:23

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.

  • Disassemble an old, broken lens was my first thought. Actually, once you've disassembled it, you've got the mounting surface - no need to make anything at all, just design your lens to meet up with the screw mounting points and you're golden. – FreeMan Sep 14 '18 at 15:57
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    @FreeMan Yes, that was the intent of the answer, although perhaps it was not clear enough. There's no need to make anything with so many old EF lenses around. I've edited to make it clearer. – Michael C Sep 14 '18 at 16:55

Canon (sort of) addresses this in the Knowledge Base article All EF and EF-S mount lenses are compatible, in which they say in part:

However, contrary to popular belief, these companies are not "licensed" to produce these lenses; instead, their designers must basically take apart and analyze EOS cameras and lenses, and then "reverse-engineer" them to fit and operate on EOS camera bodies.

They seem to be talking about both the mechanical ("to fit") and electronic ("and operate") aspects of the EF mount here. The rest of the article goes on to discuss how the EF communication protocol has changed over time to add new features while remaining backward compatible, but that third parties may need to update their products in order to remain compatible.

You're asking about the mechanical aspect of the connection, and reading between the lines in the article linked above, it seems pretty clear that you're not going to get an official specification of the mount from Canon. On the other hand, it's also clear that a number of companies have replicated the mount, and Canon seems fine with that.

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