Will Canon's FF Mirrorless be EF or EF-M Mount?

justmeMN wrote:

RubberDials wrote:

The point is not that you can't get good results adapting EF lenses to Sony but that EF mount is not suitable as a mirrorless mount for Canon.

There are a number of reasons for this which I'll go into if you want.

Please do. I can't think of any reasons. It can't be size, because both FF-DSLR and FF-Mirrorless lenses are big.

Size is one of the factors. EF mount is nearly a centimetre wider than e-mount. EF mount is actually a better size for a FF sensor but that doesn't really matter now because Sony has made a professional system work on a 46mm mount. Canon has to follow suit. EF-m mount is 47mm I believe - so they would use that.

Flange distance. As Marty shows in his illustration a mirrorless with EF mount would need to incorporate a 'spacer' to allow EF lenses to focus. Apart from the unsatisfactory nature of this - essentially you would be removing the mirror from a DSLR, rather than creating a mirrorless camera, the benefits would not outweigh the disadvantages.

It would suggest that all EF mount lenses were compatible with the camera and that would not be the case. Sony uses linear motors rather than ring motors in it's mirrorless for a reason. Mirrorless systems use hybrid focussing with contrast and phase detect. Ring motors are not best suited for contrast detect focus. The A9 cannot shoot at 20fps with all e-mount lenses. some of the older ones cannot open and close the iris fast enough. Canon's EF lens range was built over a long time. There would be many varied performance issues.

By using EF-M mount, Canon could make mirrorless lenses with linear motors like Sony and match Sony for size. The lenses would be narrower but longer to account for the smaller mount diameter.

Unfortunately doing this would immediately orphan their EF lens mount, which is also a ciné mount so that is why I don't think they'll introduce a mirrorless camera.