Canon’s New Catadioptric Lens Designs

credits: Canon

A newly surfaced Canon patent shows some unusual catadioptric zoom lens designs, and it might offer a hint at how a very fast f/1.4 zoom lens for the RF system could be built without becoming extremely large. Recently there have been multiple reports that Canon is working on a constant f/1.4 zoom, which would fit into the broader trend of increasingly fast lenses. Even Fujifilm has been exploring extremely bright designs, recently floating concepts like a 33mm f/1.0 and an 18–50mm f/1.4 as possible future lenses.

The interesting part is how Canon might actually pull something like this off. The patent, numbered 2026-033938, describes catadioptric zoom lenses designed to achieve very bright apertures. For those of you that don’t know, catadioptric designs combine traditional glass elements with mirrors that fold the light path inside the lens. Instead of traveling straight through the optics, light is reflected several times, which allows the lens to be much shorter than a conventional glass design with similar specifications. Canon has explored similar ideas before, including patents for 400mm f/3.6 and 800mm f/5 mirror lenses, although those never ended up becoming real products.

Of course, mirror lenses come with their own compromises. Because of the central secondary mirror, highlights often appear as donut-shaped bokeh, and many classic mirror lenses had fixed apertures and slightly softer rendering compared to traditional optics. The patent itself outlines several possible zoom designs, including 28–45mm f/1.2, 28–55mm f/1.4, and 35–70mm f/1.4 lenses for full-frame cameras, along with a potential 15–35mm f/1.4 APS-C version. As always with patents, these are just design concepts for now, but they do line up fairly well with the recent rumours about Canon working on a fast new RF zoom.