[Brightcolours]

Designs for  1200mm f10.5/10.6, 800mm f5.1, 400mm f3.6, 2000mm f15, 1200mm f7.6. With optical image stabilisation.
https://pdfaiw.uspto.gov/.aiw?PageNum=0&docid=20210141240

[Klaus]

I really miss a modern angle on mirror lenses. The Sony/Minolta 500mm AF f/8 was pretty cool.

[davidmanze]

For what purpose ??

[Klaus]

650g & 500mm?

[Brightcolours]

Indeed, 500mm for FF with a 13cm long lens in your bag. A 500mm f4 lens is cool and awesome to shoot sports with, but at 3 kilos or more, and a lot of bulk, you don't put that in your bag all the time. And the price...

So, why mirrorlens? Price. Size. Weight. Portability and affordability. For silly stuff like this:

[thxbb12]

Most of the time the bokeh is horrible, but it sometimes works quite well, notably for shots #2, #3 and #5.

[Klaus]

The Canon RF 600mm f/11 is sort of in the same scope. It's surely sharper but the bokeh is nothing to write home about either.

[davidmanze]

I take it there is no AF in these lenses ?..... (I couldn't see any mention of it) ...... 
 
 ....... maybe Canon is hoping the memories and disappointments of mirror-lenses's doughnut rendering and general mediocre low contrast images, that lead to their demise, have been forgotten with the coming of the generations ........


 ....... or they shrewdly applied for patents whilst waiting for some sort of AI to fill the holes in their doughnuts .........

[Brightcolours]

If they are working on such lenses, they will be AF.

[toni-a]

If they can make autofocus tilt and shift, it won't be hard to make autofocus mirror lens, especially someone already did it.
Frankly I am sure they came out with something that's why they are investing there otherwise they already have the new cheap tele primes.