I saw the PetaPixel post and studied the picture. I immediately grasped what it was all about. Then, it took me a good 10-minutes, during a leisurely walk in the dark with the dogs, to work out what it was all about.
It is NOT a lens adapter. We already have plenty of them — such as the ‘EF-EOS R Mount Adapter (with Control Ring)‘ shown above.
This is a hulking BIG convertor replete with retractable mirror, a pentaprism equivalent, an OPTICAL VIEWFINDER and maybe even a focusing unit.
When you attach it to a Canon mirrorless camera, e.g., my Canon EOS RP, via the lens mount you will have a camera with TWO (2) viewfinders — one on top of the other! One electronic (in the body of the mirrorless) and the other OPTICAL above it.
For those that insist that they have to have an optical viewfinder and to speed-up autofocusing.
But, why? Why not just get a DSLR? And that is what this seems all about.
IF Canon is serious and actually releases this, it would mean that they will no longer make high-end DSLRs! About bloody time too.
They will just make mirrorless bodies — and I am totally cool with that. I have and will continue to be committed to mirrorless.
So, in future, all the lens sensors and technology (bar faster autofocus) will be in mirrorless bodies.
Then, those that demand an optical viewfinder will have to get this convertor.
Not sure it will work in practice. The technology will work. It is pretty trivial. Even I could design one of these. Not sure anybody will pay nay good money to buy one. They will switch to Nikon.
Search ‘EOS RP’.