Patent JPO 2026-059152: Canon’s Next Move in Consumer Primes – RF 55mm f/1.8 & RF 85mm f/1.8 STM
Canon continues to flesh out its RF mount ecosystem, and a newly published patent application from Japan (JPO 2026-059152) strongly suggests the company is preparing to refresh its lineup of affordable consumer primes. While the classic “nifty fifty” has been a staple for decades, Canon’s engineers appear to be exploring a slight shift in focal lengths alongside a modernization of their mid-range portrait offerings.
The Big Picture: Why 55mm and 85mm?
For years, the RF 50mm f/1.8 STM has served as the gateway into full-frame prime shooting. However, with the RF mount maturing, Canon is finding new ways to segment its lenses.
By moving to a 55mm focal length, Canon could differentiate its next standard prime from the wider 45mm and 50mm options currently on the market. A 55mm provides a slightly tighter, incredibly flattering field of view that is highly sought after by portrait and street photographers alike.
Meanwhile, an 85mm f/1.8 STM design points toward a direct, modern alternative to the RF 85mm f/2 Macro IS STM. While the current f/2 version is highly versatile, many photographers have been holding out for a “pure” portrait lens—one that potentially trades macro capabilities for a faster f/1.8 aperture and a strictly internal focusing system for lightning-fast, silent AF during video recording.
Diving into the Patent Specs
The patent highlights several embodiments, but the 55mm and 85mm designs appear to be the most fleshed out and production-ready. Notably, these designs utilize a short back-focus distance, placing the rear elements deep inside the RF mount—a true mirrorless-first optical design.
Embodiment 1: Canon RF 55mm f/1.8 STM
This design is slightly longer than the current 50mm STM but promises an optical formula designed for modern, high-resolution sensors without relying entirely on aggressive digital corrections.
- Focal Length: 55.08mm
- Maximum Aperture: f/1.85
- Half-Angle of View: 21.44°
- Image Height: 21.64mm (Full Frame)
- Total Lens Length: 78.50mm
- Back Focus: 14.00mm
Embodiment 2: Canon RF 85mm f/1.8 STM
Unlike the current f/2 Macro, which features an extending barrel, this patent embodiment leans toward a rear-group focusing system. This is a crucial detail, as it generally allows for much faster and quieter autofocus—perfect for modern hybrid shooters.
- Focal Length: 82.50mm
- Maximum Aperture: f/1.85
- Half-Angle of View: 14.69°
- Image Height: 21.64mm (Full Frame)
- Total Lens Length: 97.83mm
- Back Focus: 15.33mm
(Bonus Find: Buried further in the same patent application is a mention of an optical formula for an RF 135mm f/2.0 STM. This would provide a much-needed, lightweight, and affordable alternative to the massive RF 135mm f/1.8L IS USM.)
When Will We See Them?
Canon patents dozens of optical formulas that never make it to the assembly line, but these specific designs fit perfectly into Canon’s current trajectory. With the focus heavily shifting toward fast, quiet STM motors for hybrid video/photo use, these f/1.8 primes feel less like experimental concepts and more like a cohesive roadmap. If these make it to production, we would expect to see them announced within the next 12 to 18 months.
What do you think of this patent? Are you ready to trade the classic 50mm for a 55mm f/1.8? Drop your thoughts in the comments below!
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via j-platpat