Something else struck me when reading the announcement of the tilt-shift adaptor patent from Canon, the patent makes it very clear that the mirrorless EOS camera the adaptor is attached to could well be a full-frame camera.
In fact, it goes even further than that, suggesting different ways that the adaptor can talk to the camera to effectively crop a full-frame sensor down to a smaller size depending on the lens that is attached and the shift/tilt.
Here’s what is says (bold emphasis added by me.)
 In S001, the camera CPU 302 detects an attachment of the interchangeable lens 100 via the adapter 200. In S002, the camera CPU 302 obtains ID (identification information) of the interchangeable lens 100 via the adapter 200. In S003, the camera CPU 302 obtains image size information of the interchangeable lens 100 from the lens information corresponding to the lens ID using a data table in the camera body 300 or the adapter 200.
 In S004, the camera CPU 302 obtains sensor size information of the camera body 300. In S005, when the camera CPU 302 determines that the image size of the interchangeable lens 100 is equal to the sensor size of the camera body 300, the flow moves to S006. Otherwise, the flow moves to S008.
 In S006, the camera CPU 302 changes a liquid crystal display range on the liquid crystal display 304 used to display an obtained image obtained from the image sensor 301 to a range in which the light is not shielded by the tilt-shift operation. In other words, the camera CPU 302 generates a signal to reduce an image pickup area of the image sensor 301 so as to make available the tilt-shift by the tilt-shift unit, when the image size of the interchangeable lens 100 is equal to the sensor size of the image sensor 301.
So, if we are reading the patent correctly the camera will have information about the image circle for every EF lens (Canon only, presumably) and will adapt the sensor area depending on the lens and the tilt-shift angle. But what’s stopping that full-frame sensor from using an EF-S lens? Absolutely nothing.
In fact, there is absolutely no good reason why a future EOS-M full-frame camera can’t use both current EF-M lenses and EF-S lenses with an adaptor. The only real reason why EF-S lenses don’t work on full-frame cameras is that the EF-S lenses protrude too far into the camera and can collide with the mirror. Of course they would only work when the camera body then crops down the sensor to APS-C size sensing while that lens is attached.
The 5DS and 5DSR already have a user-selectable crop mode to allow shooting at APS-C size to do faster shooting. The advantage of mirrorless over the traditional DSLR in this case is that this can be done with the electronic viewfinder showing the cropped image filling the view.
So here come my predictions about the future EOS full-frame camera, and the answers to all the questions you’re asking. Note these are PREDICTIONS, no more:
Will the EOS M4 be full frame?
Probably not. Canon are about to launch a new EF-M lens (EF-M 15-45mm f/3.5-6.3 IS STM) which again is a cropped sensor lens. I doubt they’d bother if they were going to skip to full-frame immediately.
But I heard the EOS M mount is too small to fit a full-frame sensor!
It’s not. It’s exactly the right size. It’s exactly the same size as the Sony E mount (as in the Sony A7 cameras) and also the same size as Nikon’s F mount. The EOS M mount was clearly designed so that it would JUST fit a full-frame sensor.
When will we see a full-frame EOS M camera?
I think the M4 (APS-C) and the M5??? (Full Frame) are likely to either be launched together or announced very closely. The Sony A7 series are eating into traditional DSLR markets and Canon need to react quickly. We will see a full-frame EOS M camera by mid 2016.
Will we see new EF-M full-frame lenses?
Yes. And I am sure Canon are now wishing the current EF-M lenses were called EF-MS because they have to think up a brand new name for their full-frame EF-M lenses. Let’s call them EF-FM for now because we have to call them something.
What will be the first EF-FM full-frame lens?
The EF-FM 50mm f/1.8 STM
Possibly followed by an EF-FM 24-70 f/4 IS STM zoom and/or a EF-FM 24-105 f/3.5-5.6 IS STM
We heard that there will be more prime lenses for EOS Mirrorless launched over the next year – I would be surprised if these aren’t designed with full-frame in mind. We may even get a situation where full-frame EF-M lenses come out before the full-frame bodies.
Will we see L glass in EF-FM lenses?
Unlikely in the first year, but who knows…
What size sensor will the M5??? have?
Hey. The three question marks aren’t part of the name. It’s to indicate I don’t know what it will be called… It may even be simply the EOS 4FM, but anyway… For it to make any sense with the cropped sensor auto mode with older EF-M lenses we’d have to assume the crop area would need to be at least 18 Megapixels. That scales out to say the sensor would need to be at least 36 megapixels. I doubt it would be much more because the files just get too large – but modern DIGIC 6 CPUs are pretty adept at handling these size of images with ease. Perhaps they’ll add a mode that essentially downsamples the 36 megapixel image to 18 megapixels essentially giving a smaller, but less noisy, image with full frame lenses but keeping the 18 megapixels for APS-C style lenses, meaning all images will be the same resolution regardless of lens type.
Will it shoot 4K video?
I think both the M4 and M5 will shoot 4K video. Hopefully, unlike the Sony A7R II, they will be able to do this without overheating too.
Will the EOS M4/M5 have electronic viewfinders built in?
I certainly hope so! However I do like the external viewfinder on the EOS M3 and the ability to angle it, I’d miss that if it was built into the camera.
Let’s come back to this article in 18 months and see how well/how badly my predictions went.
Head photo: See-ming Lee