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Gear Rumors

New EF to EF-M Adapter With Improved AF Coming From Canon? | Patent Discovered

By Anthony Thurston on February 24th 2015

Ask anyone about Canon’s mirrorless cameras, and one of the first complaints will likely be about the AF in general, but even more so when paired with EF or EF- S lenses via the Canon EF to EF-M adapter.


A new patent discovered by Egami shows that Canon could be developing another version of the adapter which would, among other things, offer an improved AF performance by EF and EF-S lenses on an EOS M body.


Patent Details

Patent Publication No. 2015-34903

  • Published 2015.2.19
  • Filing date 2013.8.9

Master lens

  • Zoom ratio 2.69
  • Focal length 72.13 135.02 193.99mm
  • Fno. 2.90
  • Half angle ω = 10.72 5.78 4.03 °
  • Image height Y = 13.66mm
  • Overall length of the lens 237.36mm
  • BF 54.00mm

Adapter installed

  • Zoom ratio 2.69
  • The focal length f = 72.12 135.00 193.96mm
  • Fno. 2.90
  • Half angle ω = 10.72 5.78 4.03 °
  • Image height Y = 13.66mm
  • Overall length of the lens 239.70mm
  • BF 16.77mm

Canon patent

  • Fast AF adapter
  • Wobbling corresponding
  • 3-group configuration of positive and negative positive
  • 2 group also serves as a focus group and the anti-vibration group
  • And realize high-speed AF focus group was lighter

Personally, I feel like this sort of a futile effort given the current crop of EOS M cameras. They are all way too small to make using full sized EF lenses practical. If Canon has any larger, more SLR styled mirrorless cameras (a la Fuji X-T1), then I feel that an adapter like this would make much more sense.

That said, the AF with the current adapter is pretty poor. Users can autofocus fairly well on Sony cameras with the EOS adapters they have, so you would think – if for a matter of pride alone – that Canon could produce an adapter that gave good AF performance on their own mirrorless cameras.

Anyway, it will be interesting to see what comes of this.

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Anthony Thurston is a photographer based in the Salem, Oregon area specializing in Boudoir. He recently started a new project, Fiercely Boudoir to help support the growing boudoir community. Find him over on Instagram. You may also connect with him via Email.

Q&A Discussions

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  1. Anders Madsen

    I’m kinda left scratching my head here. If Canon intends for customers to use adapted lenses anyway, why did they go through all the trouble of creating a new, non-backwards compatible mount in the first place?

    And yes, I know that there are native EF-M mount lenses out there, but they are so few (even after three years on the market) that Canon couldn’t really be more half-assed about it, even if they tried. If they really wanted to look like they care about the M-series, they need to offer up some lenses that a) makes the size difference compared to full frame and APS-C stand out and b) actually has an AF that works well enough to be practically usable – something that an adapted lens really doesn’t.

    I’m aware that the patent is meant to at least mitigate b), but it’s still half-assed when it comes to size and totally negates the most cited reason for mirrorless to exist in the first place: The reduced size and weight. For that to come into play, EF-M mount lenses are critical.

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  2. Derek Schwartz

    Anthony your point about handling of the current M bodies doesn’t make it comfortable to use bigger lenses; I have an adapter for my M1, and slapping a 70-200 on it is just shy of ridiculous since I have to switch up how to hold the lens/body combo basically using the lens to support everything. This is true even with the wonderful aluminum grip I got for my M from Richard Franiec. That said, it looks like the M3 may be a move more towards the XT-1 with a MUCH better integral grip…so maybe the idea of bigger lenses isn’t quite so bonkers?

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  3. Hannu Siika-aho

    Maybe not totally futile effort. You will have better edge/corner performance thanks to the larger image circle EF/EF-S lenses cover.

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    • Anthony Thurston

      I agree, the idea of it, and in some practices it would be nice. But in actual use, the EF lenses on the current crop of M bodies is hard to handle. If they end up making bigger M bodies add extra grips or something then I think it would be a much more realistic option for more general use.

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