Just when patents get published is based largely on statutory time periods, and sometimes the products themselves come out before publications, as is the case with the well-liked Canon RF 100-500 and the two 70-200mm lenses Canon added to the RF lineup. Today the patent finally squirted out of Japan’s patent office (via An image on a sensor).

In addition to those three lenses, other embodiments were explicitly laid out, including some cheaper, darker zoom lenses ranging up to f/8 and, very interestingly, a crop 55-250mm with variable aperture between 4.5 and 6.3 (roughly).

The patents were filed back in 2019, back when the M mount series didn’t appear in quite so much trouble. The crop sensor zoom may have been intended for that mount, or – to the joy of the disheartened RF crop boosters – it could mean that something in the crop sensor flavor may have been in the planning stages back then.

Looking at Canon’s published designs for the 100-500 zoom, the second embodiment of the patent matches the lens arrangement precisely.

The patent design
As manufactured, the RF 70-200mm f/2.8

The third embodiment matches exactly the RF 70-200 f/2.8, and the first embodiment matches the RF 70-200 f/4.