Canon Patent for Consumer APS-C RF-S Primes
We have long wanted RF-S or Canon RF cropped sensor primes, and so far, at least, Canon has been resistant. Fortunately for us, Sigma has released some excellent primes for Canon's RF-S cameras. In this patent application (2026-052804), Canon shows us quite a few embodiments for cropped sensors.
All of the designs rely on image stretching to fill the entire sensor, some of them quite significantly. So I assume that these are meant to be low-cost, bang-for-the-buck lenses where you are willing to take on some optical compromises to get a prime lens with the Canon name on it. The usual half image height for APS-C cropped sensors is 13.66mm, and some of these designs are all the way down into 11.5mm.
It could also be that these lenses are not designed for APS-C cameras, but for smaller sensor cameras in security systems, etc. However, I still believe that Canon assumes multi-use for its patent applications, so I'll assume that there is a cropped RF-S intent in these designs.
Canon RF-S 12mm f/2.8 STM
This is a nice, small 12mm (19mm equivalent) prime that relies on a significant amount of corner stretching.
Embodiment Specifications
| Focal length |
28.17 |
| F-number |
2.83 |
| Half angle of view (°) |
24.14 |
| Image height |
12.63 |
| Lens length |
67.03 |
| Back Focus Distance |
15.32 |
Canon RF-S 28mm f/2.8 STM
This embodiment shows a 28mm or 45mm equivalent prime with a lens length of around 55mm.
Embodiment Specifications
| Focal length |
28.17 |
| F-number |
2.83 |
| Half angle of view (°) |
24.14 |
| Image height |
12.63 |
| Lens length |
67.03 |
| Back Focus Distance |
15.32 |
Canon RF-S 10mm f/2.8 STM
This embodiment shows a 10mm or 16mm equivalent prime with a lens length of around 53mm. I would absolutely purchase this lens.
Embodiment Specifications
| Focal length |
10.02 |
| F-number |
2.83 |
| Half angle of view (°) |
48.98 |
| Image height |
11.52 |
| Lens length |
65.00 |
| Back Focus Distance |
12.00 |
Canon RF-S 14mm f/2.8 STM
This embodiment shows a 14mm or 22mm equivalent prime with a lens length of around 48mm.
| Focal length |
14.63 |
| F-number |
2.83 |
| Half angle of view (°) |
39.45 |
| Image height |
12.04 |
| Lens length |
64.29 |
| Back Focus Distance |
16.54 |
Canon RF-S 18mm f/2.8 STM
This embodiment shows an 18mm or 28mm equivalent prime with a lens length of around 58mm.
| Focal length |
18.13 |
| F-number |
2.83 |
| Half angle of view (°) |
33.83 |
| Image height |
12.15 |
| Lens length |
70.71 |
| Back Focus Distance |
12.17 |
Closing Thoughts
We have seen Canon do sweeping wide patents before for optical designs, and nothing has come out of them. So I'm not going to go all clickbait and suggest that Canon will come out with 4 RF-S primes in the next year.
It's good that Canon is researching and applying for optical design patents in this domain, which may mean it's starting to develop primes for RF-S users. These are also rather slow primes, and while for an ultra-wide lens such as a 10mm f/2.8 this is absolutely suitable, for longer focal lengths, it would be nice if they released f/2 or f/1.4 primes instead.
Just a Reminder
With all patents and patent applications, I have to stress constantly – this is simply a look into Canon’s research; the only thing we can quantify accurately is that Canon is researching this. A patent application doesn’t mean they are going to release this in the next month, or even year, or even at all.
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