Canon Patent Reveals Possible RF 300mm f/2.0L and RF 200mm f/1.8L Lenses
A recent patent application by Canon (JP-2025-179579) has surfaced, detailing optical formulas for two incredibly fast super-telephoto prime lenses: a 300mm f/2.0 and a 200mm f/1.8.
These specs will be familiar to long-time Canon shooters. The EF 200mm f/1.8L USM, affectionately known as the “Eye of Sauron,” is a legendary lens. The EF 300mm f/2.8L IS USM is a staple of sports and wildlife photography, but a 300mm at f/2.0 is a different beast entirely, previously seen in the rare and expensive EF 300mm f/2.8L IS USM’s predecessor, the FD 300mm f/2.8L.
If these lenses come to fruition for the RF mount, they would be absolute behemoths in terms of both size and optical performance. Let’s take a closer look at the details.
The Optical Designs
The patent details two distinct optical formulas, which we’ll call Example 1 and Example 2.
Example 1: The 300mm f/2.0
This is the star of the show. A 300mm lens with a maximum aperture of f/2.0 is an engineering marvel. It would allow for incredibly fast shutter speeds in low light and produce a razor-thin depth of field, completely obliterating backgrounds.
- Focal Length: 292.50 mm
- F-number: 2.06
- Half Angle of View: 4.23 degrees
- Image Height: 21.64 mm
- Lens Length: 350.13 mm
- Back Focus: 13.50 mm
This lens design consists of 16 elements in 11 groups. As you can see from the lens block diagram below, it features a massive front element and a complex arrangement of glass to correct for aberrations.
Example 2: The 200mm f/1.8
This is a spiritual successor to the legendary EF 200mm f/1.8L. It’s a shorter, slightly faster lens than the 300mm, and it’s a favorite focal length for portrait and indoor sports photographers.
- Focal Length: 195.00 mm
- F-number: 1.85
- Half Angle of View: 6.33 degrees
- Image Height: 21.64 mm
- Lens Length: 250.00 mm
- Back Focus: 13.50 mm
This design is slightly simpler, with 14 elements in 11 groups, but it’s still a complex piece of optical engineering.
Optical Performance
The patent also provides aberration charts for these lenses. The charts for the 300mm f/2.0 (Example 1) show excellent correction for spherical aberration, astigmatism, and distortion, as you would expect from a high-end L-series lens.
Advanced Focusing System
A key feature mentioned in the patent is a sophisticated inner focusing system. To achieve fast and accurate autofocus with such large and heavy glass elements, the patent describes a mechanism where two separate lens groups are moved.
- First Focusing Group: This group is located towards the front of the lens.
- Second Focusing Group: This group is located further back, near the image plane.
By moving these two groups independently, the lens can achieve faster autofocus speeds and maintain high image quality throughout the focusing range, from infinity to close-up. This is a common technique in modern, high-performance telephoto lenses.
Conclusion
While a patent filing is never a guarantee that a product will come to market, it’s exciting to see Canon researching such ambitious lenses for the RF mount. An RF 300mm f/2.0L or RF 200mm f/1.8L would be a dream come true for many professional photographers. They would be large, heavy, and undoubtedly expensive, but the optical performance and creative possibilities would be unmatched. We’ll be keeping a close eye on any further developments.
What are your thoughts? Would you be interested in either of these lenses? Let us know in the comments below!