Converting A Sigma Lens To Canon, Digital Functionality Included

These days, camera lenses aren’t just simple bits of glass in sliding metal or plastic housings. They’ve often got a whole bunch of electronics built in as well. [Dan K] had just such a lens from Sigma, but wanted to get it working fully with a camera using the Canon EF lens fitting. Hacking ensued.

The lens in question was a Sigma 15-30mm f/3.5-4.5 EX DG, built to work with a Sigma camera using the SA mount. As it turns out, the SA mount is actually based on the Canon EF mount, using the same communications methods and having a similar contact block. However, it uses a mechanically different mounting bayonet, making the two incompatible.

[Dan] sourced a damaged EF lens to provide its mount, and modified it on a lathe to suit the Sigma lens. A short length of ribbon cable was then used to connect the lens’s PCB to the EF mount’s contacts. When carefully put back together, the lens worked perfectly, with functional auto-focus and all.

It goes to show that a little research can reveal possibilities for hacking that we might otherwise have missed. [Dan] was able to get his lens up and running on a new camera, and has taken many wonderful pictures with it since.

We’ve seen some great lens hacks over the years, from 3D printed adapters to anamorphic adapters that create beautiful results. If you’ve got your own mad camera hacks brewing up, drop us a line!

8 thoughts on “Converting A Sigma Lens To Canon, Digital Functionality Included

  1. That’s my work, I’ll try and answer any questions, but if I miss them (or it’s years later and you are attempting the same thing) contact me on twitter (@ZDP189).

    1. I have two Sigma SA mount lenses I wish I could use on my Canon 700D, however these lenses do not fit on the Canon mount. When I saw this article, I got excited, I thought a fix has come at last, however I don’t have the know how to do this conversion, so I guess my Sigma lenses will be left in cupboard, nevermind.

      1. It’s been a few years, but if I remember right, they used some kind of hybrid bayonet similar to PK, but with Canon EOS contacts and protocol. So you can use your SA lenses on an EOS body, but you’ll need to change the bayonet as I did here.

    1. There has been some projects that let you use EOS lenses controlled via microcontroller, featured on HAD if I recall correctly, so find those projects and you can at least mount a lens that speaks Canon lens to other camera or mount if you know what your camera is demanding of the lens.

      I don’t recall ever seeing anybody talking to other lens though, but that doesn’t mean anything much.

    2. Sigma figured out Canon EOS recognition and control protocols for making their third party lenses. When it came to making their own lenses for their own bodies, they adopted Canon protocols, rather than reinvent the wheel. Hence, all the intellectual work was already done and it was just a matter of literally hacking a bayonet off an donor lens, thinning it to fit and screwing it onto the Sigma lens.

  2. Are there any issues in case the adaptation results in the lens not sitting in the exact intended distance from the sensor? Does the autofocus correct for that?

  3. Hi! Is there a tutorial somewhere on how to convert a Sigma SA mount BODY to EF? That would open up a lot of possibilities…
    I have a Sigma sdQ. Love the camera but mounting Sigma EF glass would be so much cheaper that sourcing their SA equivalent.

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