This patent application (2024-101645) has a bunch of embodiments, allowing us to frame some observations about optical designs that we occasionally see here.
It seems very likely that the first embodiment in this patent application is the RF 10-20mm f/4L IS STM.
In short, if this is correct – I was wrong. Yes, we need to pause and consider the significance of that statement. For starters, Craig is going to screenshot this and truck it out all the time. Right up there with the time I accidentally toasted the home page to the website.
The embodiment shows that the lens back focus distance is down to 12mm – which suddenly shows that Canon can design lenses to sit further back into the lens without a problem. I may be miffed about the stretching but in the case of the 10mm, it’s a great optic that doesn’t seem to show a loss by use of digital manipulation and Canon certainly doesn’t seem to feel any guilt about slapping a 2299 price tag on the said lens. So, this technique is no longer used on cheap lenses. To be fair though, the amount of stretching on this lens is at an extreme wide angle, and at 10mm that’s easily manageable. So in summary, 12mm back focus distances and stretching are here to stay even in the world of L lenses.
Curiously, this patent application was filed on January 18, 2023, the RF 10-20mm f/4L IS STM was announced on October 13, 2023. We are just seeing the patent application published for public view now, a little over 18 months after the filing.
The purpose of this patent application according to Canon is to have image stabilization work effectively across the entire image circle with extreme ultra wide focal lengths. I didn’t really think of this as a problem, but apparently it is.
The amount of image blurring differs between the center and the periphery of a photographed image. In particular, the wider the angle of the zoom lens, the greater the change in perspective, so the amount of image blurring in the periphery of the image becomes larger than in the center of the image. In the zoom lens of Patent Document 1, even if the image blurring in the center of the image is corrected, the image blurring in the periphery of the image remains. The object of the present invention is to provide a lens device having good optical characteristics even during anti-vibration.
Canon RF 10-20mm F4.0 IS STM
This is the RF 10-20mm F4L IS STM. See? Some of these patent applications do demonstrate real-world lenses.
| Wide Angle | Medium | Telephoto | |
| Focal length | 10.33 | 15.00 | 19.39 |
| F-Number | 4.08 | 4.08 | 4.12 |
| Half Angle of View | 61.36 | 55.26 | 48.13 |
| Image Height | 18.92 | 21.64 | 21.64 |
| Lens Length | 128.82 | 122.35 | 123.27 |
| Back Focus Distance | 12.13 | 12.13 | 12.13 |
Canon RF 9-18mm F4 IS
This would have been another impressive ultra wide zoom if Canon decided on this design, interestingly it’s a little more tighter on the backfocus distance – I wonder if the threshold is 12mm for Canon – and thus, this embodiment didn’t make it past the design stage.
| Wide Angle | Medium | Telephoto | |
| Focal length | 9.20 | 16.04 | 17.90 |
| F-Number | 4.08 | 4.08 | 4.12 |
| Half Angle of View | 64.04 | 53.45 | 50.40 |
| Image Height | 18.90 | 21.64 | 21.64 |
| Lens Length | 125.26 | 118.57 | 119.35 |
| Back Focus Distance | 10.50 | 10.50 | 10.50 |
Canon RF 11-24mm F4 IS
This is a lens that is similar to the 11-24mm F4 of the EF mount, and I wonder if Canon’s initial thoughts were focused on this lens before deciding to go that little bit wider with the 10mm and a more compact zoom range.
| Wide Angle | Medium | Telephoto | |
| Focal length | 11.30 | 16.61 | 23.90 |
| F-Number | 4.08 | 4.08 | 4.12 |
| Half Angle of View | 59.29 | 52.49 | 42.15 |
| Image Height | 19.02 | 21.64 | 21.64 |
| Lens Length | 129.79 | 125.70 | 129.33 |
| Back Focus Distance | 14.54 | 12.80 | 10.54 |
Canon RF 11-22mm F2.8 IS
This would be a big and heavy lens, and certainly one that would take a huge chunk out of your wallet – but an 11-22mm F2.8L would be welcomed especially for astro-landscapes.
Interestingly, the optical layout is very similar to the Canon 10-20mm f/4L IS STM except L5 has an additional element.
| Wide Angle | Medium | Telephoto | |
| Focal length | 11.30 | 14.97 | 22.00 |
| F-Number | 2.89 | 2.89 | 2.89 |
| Half Angle of View | 59.44 | 55.32 | 44.52 |
| Image Height | 19.14 | 21.64 | 21.64 |
| Lens Length | 137.35 | 129.65 | 125.58 |
| Back Focus Distance | 13.50 | 12.41 | 10.54 |
Canon RF 10-20mm F2.8-4 IS
In this patent application, Canon has already shown us the 10-20mm that they decided on, but this is another design that would have been interesting to see make it into production.
| Wide Angle | Medium | Telephoto | |
| Focal length | 10.30 | 15.22 | 19.80 |
| F-Number | 2.89 | 3.50 | 4.12 |
| Half Angle of View | 61.76 | 54.87 | 47.54 |
| Image Height | 19.18 | 21.64 | 21.64 |
| Lens Length | 132.94 | 126.11 | 127.01 |
| Back Focus Distance | 11.35 | 11.35 | 11.35 |
As with all patent applications, this is a look into Canon’s ongoing research.
Japan Patent Application 2024-101645
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I'm also an ultra wide bigot, i find them more interesting ;)
I think they can make one.