Canon Patent: Compact APS-C Wide Primes — 10mm, 12mm, 18mm & 28mm F2.8

Canon has filed a patent application (publication number P2026052804, published March 25, 2026, filed September 12, 2024) covering optical systems that look suspiciously like a lineup of compact APS-C prime lenses. The patent — titled simply "Optical System and Imaging Device" — presents multiple embodiments clustered around an F/2.8 aperture class, covering focal lengths from 10mm to 28mm.

Here's what the optical data tells us:

Embodiment 1 — ~12mm F2.8

• Focal length: 12.38mm
• F-number: 2.83
• Half angle of view: 42.99°
• Image height: 11.54mm
• Total length: 63.50mm
• Back focus: 12.00mm

Embodiment 3 — ~28mm F2.8

• Focal length: 28.17mm
• F-number: 2.83
• Half angle of view: 24.14°
• Image height: 12.63mm
• Total length: 67.03mm
• Back focus: 15.32mm

Embodiment 4 — ~10mm F2.8

• Focal length: 10.02mm
• F-number: 2.83
• Half angle of view: 48.98°
• Image height: 11.52mm
• Total length: 65.00mm
• Back focus: 12.00mm

Embodiment 7 — ~14mm F2.8

• Focal length: 14.63mm
• F-number: 2.83
• Half angle of view: 39.45°
• Image height: 12.04mm
• Total length: 64.29mm
• Back focus: 16.54mm

Embodiment 8 — ~18mm F2.8

• Focal length: 18.13mm
• F-number: 2.83
• Half angle of view: 33.83°
• Image height: 12.15mm
• Total length: 70.71mm
• Back focus: 12.17mm

What's Canon Up To?

A few things stand out immediately. All embodiments share a tight F/2.83 aperture — clearly a unified F2.8 optical design philosophy across the series. The total lengths are remarkably compact: sub-70mm for everything from 10mm to 28mm is impressive. These aren't the kind of chunky pro primes Canon builds for RF full-frame.

The image heights are the interesting wrinkle. At 11–12mm image height, these designs fall short of what you'd normally expect for APS-C (which typically needs ~14mm image height). Asobinet's own analysis notes this discrepancy, suggesting Canon may be designing these with some built-in cropping in mind — trading a bit of the corner image circle to correct residual distortion in-camera. This isn't unusual; several existing Canon lenses do exactly this.

The back focus situation: With back focus values of 12–15mm across the lineup, these are clearly designed for a short flange-to-sensor distance mount. That points firmly at EF-M or RF-S / EOS R APS-C territory. Canon's EF-M system is effectively on life support at this point, so RF-S is the logical destination — meaning these could be affordable compact primes for the EOS R50 / R10 / R100 crowd.

Does This Mean Anything?

As always with Canon patents: file with healthy skepticism. Canon patents prolifically, and the vast majority never leave the lab. That said, this is a coherent, well-structured lineup — five focal lengths with unified aperture and compact dimensions — which suggests someone at Canon was seriously thinking about a kit of compact APS-C primes. Whether that becomes RF-S 10mm F2.8, 12mm F2.8, 18mm F2.8, and 28mm F2.8 lenses is another question entirely.

What Canon has shown with the RF-S line so far is a willingness to offer affordable, small lenses for their crop-sensor mirrorless bodies. A set of fast-ish primes in this style would fill a real gap in the RF-S lineup, which currently leans heavily on zooms. Fingers crossed this one actually makes it to production.

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Source: Asobinet (Japanese) — Patent P2026052804