A recent patent filing shows Canon is developing new catadioptric, or mirror, lenses for full-frame cameras. This old-school optical design uses both refractive glass and reflective mirrors to fold the light path, allowing for much shorter and more compact lenses compared to traditional designs.
The patent includes designs for full-frame zooms like a 28-45mm f/1.2 and a 35-70mm f/1.4. These unusually bright apertures for zooms suggest Canon may be trying to combine high speed with a small form factor. Typically, catadioptric designs are used in long telephoto primes, but these patents indicate a shift towards wider, everyday focal lengths.
While mirror lenses often have drawbacks like fixed apertures and potential image quality issues, Canon's research could aim to overcome these for future EOS R system cameras. It's also possible the designs are for a new fixed-lens compact camera. However, patents don't always lead to products, and Canon files thousands annually, leading the industry in innovation for decades.