At first, when I was writing up this patent application (2024-082112), I was leaning toward what others are mentioning on the internet that these are for ILC (interchangeable lens cameras) but after reading more, and looking at the back focus distances involved, I think it’s more likely that these are for a compact rangefinder styled APS-C or full-frame camera.
All these lenses have back focus distances which would have the lens sticking nearly 8 to 9mm into the camera, with the rear optical element being the largest. The element design is similar to the existing lenses, such as the EOS RF 28mm f/2.8 STM. But the EOS RF 28mm f/2.8 STM has far less ingress into the mount.
So taking everything into account, I believe rules these out as RF and RF-S lenses.
Canon Full Frame 28mm F2.8
| Focal Length | 28.50 |
| F-Number | 2.86 |
| Half Angle of View | 37.20 |
| Image Height | 21.64 |
| Lens Length | 42.64 |
| Back Focus Distance | 13.25 |
Canon Full Frame 24mm F2.8
| Focal Length | 24.50 |
| F-Number | 2.88 |
| Half Angle of View | 41.45 |
| Image Height | 21.64 |
| Lens Length | 47.90 |
| Back Focus Distance | 11.28 |
Canon 33mm F1.8 APS-C
This one is curious though, because it’s a 50mm which seems a little long for a compact, and it’s a complicated design. It should be noted that the near-perfect optically EF-M 32mm f/1.4 STM was far more complex.
| Focal Length | 33.08 |
| F-Number | 1.85 |
| Half Angle of View | 22.44 |
| Image Height | 13.66 |
| Lens Length | 41.00 |
| Back Focus Distance | 11.91 |
As with every single patent application nothing discussed here is guaranteed to make it into production, or even a real patent as there are still many patent process steps yet to finalize the patent application. This is simply a look into the research and development that Canon is doing.
Source: Japan Patent Application 2024-082112
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(Sorry, didn't have the time for detailed searching and comparing)
But I'd take a similar 24mm pancake, too.
And a friend surely would like to pair that 33mm F1.8 APS-C with his R7 ;)
RF 28/2.8 block diagram:
Sorry, Richard...looks like there might be something more you need to take into account... ;)
I was about to do it later, but you came first ;)
Of course, it directly pops out that the shape of the fourth element seems to be more complex in the RF 28/2.8 block diagram.
Generally, the second group seems to be a bit more complex in the final design.
But I suppose that this was a change in development during the final design of the RF28/2.8
Fluorite, Aspherical, UD and BR Lenses
I think the current-production lens cannot be that shown as an example embodiment of the lens formula patent:
1) You cannot patent something that's already public, even if you make it. It has to be secret. I imagine there's some special cases if it's public due to someone leaking it, etc., but a current product would be absolutely impossible.
2) Both diagrams are strictly informational and need not match the actual patent and product's elements' shapes and dimensions religiously. That said, the diagrams are similar... but differ. Counting from the front, elements 4 and 5 are clearly far smaller in the application while 1 and 2 are bigger. It's not just a question of pixels of difference here, for instance plausibly due to the printout resolution, but substantially different.
You need to read up on the patent process. What we’re looking at is a published patent application that was filed 18 months ago. It published on June 19, 2024 meaning it was filed on December 19, 2022. That’s the date before which prior art is actually prior. Was the RF 28/2.8 a launched product on Dec 19, 2022? No.
Yes, and the first part explains the second. Diagrams in a patent are examples, as long as the product satisfies the claims in the patent, it’s covered by the patent. It’s normal for slight design changes to be made as a patented invention moves into mass production.
Sure. What's patented here is the mathematical model of the lens formula, not the example embodiments. I used to remind the group admin of that every six months or so.
I worked on a half-dozen Japanese patents in the 1990s at Omron, before I switched to finance. I can't think of why I'd need to learn more about it.
But the EF-M lenses ARE mirrorless designs, with very short film-to-flange distances. They can't be used on cameras with mirrors, unlike EF-S, right? So an EF-M has basically all the design freedom an RF-S does.
If it is legitimately lighter and cheaper and not suffering in some other way (bigger, less sturdy, slower AF, more aberrations, worse OOF bokeh, etc.), that'd be real news. The only things I can think of are that RF lenses no longer have to care about vignetting or distortion, since these can be undetectably*** fixed digitally. It's possible that new lenses are letting these two metrics slide into the wastecan, and using the resulting freedom to improve every other aspect of the lens (e.g., making it lighter AND cheaper AND higher resolution AND lower aberration AND better OOF highlights etc.).
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*** I know others say differently but I've asked on this forum politely for counterexamples 50 times and the only counterexample to my statement that I've seen was Milky Way astrophotography where vignetting correction caused a bit more visual noise in the far corners. I totally recognize that as an exception to my statement above, but I would also say that it's a very very unusual and specific case where ISO is already very high, corners EXCEEDINGLY dark, aperture already fully wide, and not much freedom to lengthen exposure, on top of using an ultra-wide angle lens which are typically more prone to cos^4 vignetting on top of other vignetting. Remove any one of those factors, and the digital correction of vignetting would have no visible effect. EG if ISO were lower, no noise. If corners were zone III+, no noise. If aperture not fully open, you could open up, reduce ISO, and no noise. If the subject weren't in very slow motion, you can use a longer exposure, and lower ISO, so no noise.
And as for distortion correction I've had lots of people proudly say that the distortion correction lowered image quality too far for their exacting requirements, but never have seen an actual example of something where you can even tell it was in use.
The EF-M lens has 14 elements (including one Glass Molded Aspheric). The design in the patent has only seven elements and appears to have at least two and possibly three molded elements that may well be some kind of optical plastic. The back two are much more aggressively aspheric than traditional glass molded aspherics. That change in technology would account for my initial comment, "lighter and possibly cheaper, with excellent performance". The RF 28mm makes that case very effectively. Are electronic corrections being thrown into the mix as well? Possibly, but the 28 is pretty decent without that. Molded lenses are the way phones make cheap and quite good (for the size of the imager) cameras. Molded lenses are very cheap to manufacture once you have invested in the outrageously expensive mold (and Canon may well have developed a way to make the molds less expensively).